Document kDp5xEn6oOYd6BgnOGwoja1EV

REVIEW ARTICLE Plasma Cell Myeloma-New Biological Insights and Advances in Therapy By Bart Barlogie, Joshua Epstein, Peter P LASMA CELL myeloma has been the prototype of a monoclonal tumor cell proliferation that reveals a monoclonal protein in the serum or urine in more than 90% of patients. The disease spans a spectrum of clinical entities, including localized and disseminated, as well as indolent and aggressive forms.t3 Patients typically suffer from painful fractures, anemia or renal failure, and from recurrent infec- tions associated with immunodeficiency. With a median age of 60 years, current treatments have been palliative rather than curative.5 Thus complete remissions from standard alkylating agent-glucocorticoid programs have been achieved infrequently, and all patients succumb after a median of about 3 years, even though about 10% of current patients will survive 10 years.6 During the past 5 years, new insights have been gained of the cellular and molecular biology of myeloma, so that the previous notion of a terminally differentiated B-cell malig- nancy is giving way to the provocative concept of an early hematopoietic stem-cell disorder manifesting itself mainly at the mature stage of B-cell lineage. Therapeutically the growth-controlling effects of alpha-interferon7 and the feasi- bility of hematopoietic stem-cell-supported high-dose cyto- toxic regimens8 have raised hope for a fundamental change in prognosis that had been stagnant since the introduction of melphalan and prednisone some 25 years 9t This review summarizes data that myeloma may be an early stem-cell disorder; describes features that predict clinical outcome; and reviews marrow-ablative programs for patients with newly diagnosed and refractory disease. Readers with inter- est in traditional staging and treatments are referred to other recent 2t 5 Genotypic Studies MYELOMA BIOLOGY Because of the low fraction of cells in DNA synthesis, few mitoses are usually available to define karyotype abnormali- ties.t6tl Unlike results in leukemia and lymphoma, disease- specific anomalies have not yet been identified; the presence of complex numeric and structural rearrangements suggests a long disease course with many acquired genetic changes. Analysis of nuclear DNA content by flow cytometry (that does not depend on mitoses) has demonstrated aneuploidy in 80% of patients; hyperdiploidy was most frequent (70% of total, with a DNA excess of 10% to 20%); diploidy was present in 20%; and hypodiploidy in about lO%.t820 Also confirmed by cytogenetic studies, DNA-hypodiploidy was associated frequently with only light-chain production and with resistance to standard therapies. (Table i).t72t Chromo- somal translocations, as in non-Hodgkin's lymphoma, were found in about 10% ofcases, and t(8;14) abnormalities were associated with an IgA isotype.t7 Deletions ofthe long arm of chromosome 6 have recently been linked to lytic bone disease.22 An adriamycin-resistant myeloma cell line (8226/ DOX) displaying the multidrug resistance (MDR) pheno- type has a deletion of the long arm of chromosome 7,23 which is the site of the p-glycoprotein gene.24 Selvanayagam, and Raymond Alexanian While the acquisition of new DNA stemlines on flow cytometry is rare,25 this technique is insensitive for the detection of structural aberrations or small numeric chromo- somal abnormalities.26 Indeed, the typical complexity of plasma cell karyotype suggests that clonal evolution must be common. With the prospect of better in vitro culture meth- ods, the authors expect that primary and evolutionary karyo- typic anomalies will be identified regularly in myeloma progenitor cells. Such information may help define discrete disease entities and direct research into the molecular mech- anisms of abnormal growth and differentiation. Cell Kinetics and In Vitro Growth of Tumor Cells Laboratory methods for cytokinetic studies have been refined, so that autoradiography with tritiated thymidine has been replaced by the more convenient bromodeoxyuridine (BUdR) immunofluorescence technique.27'28 As expected in a tumor composed mainly of terminally differentiated B cells (ie, plasma cells), the labeling index after in vitro pulse exposure is usually low, with average values of 1% at diagnosis and higher values at relapse.29 Both autoradio- graphic and BUdR techniques have identified even lower labeling indices in patients with monoclonal gammopathy of unknown significance (MGUS) and indolent myeloma.3#{176}32 A similar discrimination also resulted from the study of B lymphocytes in peripheral blood.32'33 In patients with symp- tomatic myeloma, higher values of plasma-cell labeling index were associated with shorter survival time, independent of tumor mass.336 Relative to values at diagnosis, tumor cell-growth fraction (determined from tritiated thymidine administration in vivo) was much higher during relapse,37 when in vitro colony growth is also more successful. The recent availability of antibodies that distinguish different DNA precursor mole- cules (BUdR and IUdR) permits a more expedient immuno- fluorescence-based analysis by flow cytometry of cell-cycle time parameters and growth fraction (J Gray, personal communication, June 1988). Several studies are currently in progress in myeloma and other malignancies to define the value of Ki-67 monoclonal antibody (MoAb) as a means of assessing the fraction of cells capable of cell prolifera- tion 38,39 Consistent with the low proliferative activity of typical plasma-cell myeloma, attempts at establishing long-term From the University of Texas M.D. Anderson Cancer Center. Department ofHematology. Houston. Submitted September 20. 1988; accepted November 18, 1988. Supported in part by Grants CA37161 and CA28771 from the National Cancer Institute, National Institutes ofHealth, Bethesda. MD. Address reprint requests to Bar: Barlogie. MD. Department of Hematology. M.D. Anderson Hospital & Tumor Institute, Univer- sity of Texas Box 30. 1515 Holcombe Blvd. Houston. TX 77030. itt 1989 by Grune & Stratton, Inc. 0006-4971/89/7304-0021$3.00/0 Blood, Vol 73, No 4 (March), 1989: pp 865-879 865 866 Cytogenetic Abnormality Hypodiploidy t (8;14) 6q7q Trisomy (q24;q32) 11 Table 1. Clinically Relevant Chromosomal Anomalies % Incidence Associations 10 Only Bence Jones protein Primary drug resistance <5 IgA 15 Lytic bone disease ? Drug resistance, site of mdr gene 10 Decreased p21 (H-ras) levels BARLOGIE ET AL Reference 17 21 17 22 23 111 cultures have met with limited success, so that only about a dozen human myeloma cell lines are now available, often with unusual phenotypic features typical of earlier stages of maturation."#{176} Similar problems were met in sustaining short- term cultures for the study of in vitro drug sensitivity.41'42 Systematic laboratory efforts by Dune et al (BGM Dune, personal communication, October 1987) have since led to the recognition that monocytes and CD4-positive I cells provide important stimuli for in vitro growth of plasma cells and their precursors, while CD8-positive suppressor I cells seemed to inhibit growth. Employing a double-layer agar technique with irradiated HL-60 feeder cells, Millar et al.43 reported successful myeloma colony growth in almost 90% of patients. Several cytokines are involved in the proliferation and differentiation of normal munine and human B cells.'45 After B-cell activation by interleukin-4 (IL-4)''47 and expansion by interleukin-5 (IL-S),48 B-cell stimulatory factor 2 (BSF-2) induces the final maturation of B cells into immunoglobulin-secreting plasma cells.49 Based on studies of DNA sequence homology, BSF-2, intenfenon-beta-2, and hybnidoma-plasmacytoma growth factor represent the same cytokine that is now termed interleukin-6 (IL-6).50'5' Pro- duced by monocytes, fibroblasts, and 1-cell lines, the domi- nant action of IL-6 is the differentiation of activated B cells, although effects on normal hematopoietic stem cells (in concert with IL-3) have also been reported.52'53 IL-6 probably accounts for the promotion of human myeloma growth by conditioned medium from adherent spleen cells when Balb/c mice were primed by intrapenitoneal injections of pnistane or mineral oil.4' The recent demonstration that fresh myeloma cells produced IL-6 constitutively and expressed IL-6 necep- ton (IL-6R), with stimulation of DNA synthesis by exoge- nous IL-6 in some cases has suggested that IL-6 may function as an autocnine growth factor.54 This observation has been questioned by Klein et al,55 who noted that IL-6 activity resided entirely in bone marrow-adherent cells and favored a paracnine growth mechanism. These authors had previously reported an autocnine function for BCGF II (IL-5) in human RPMI 8226 cells.56 Investigating the molec- ular basis of growth factor and receptor gene activation should clarify the pivotal mechanisms involved in the abnor- mal proliferation and maturation of plasma-cell myeloma. Tumor Phenotype While an individual patient has fairly uniform plasma cell morphology, there is moderate heterogeneity among dif- ferent patients. The Mayo Clinic group has distinguished between plasmacytic, lymphoid, and plasmablastic variants with progressively increasing labeling index and adverse prognosis.30'57 As a tumor perceived to be composed of terminally differentiated B cells with commitment to immu- noglobulin production and secretion, plasma-cell myeloma is composed mainly of cells that contain monoclonal cytoplas- mic immunoglobulin.58 Monoclonal clg expression by diploid cells in about 20% of patients with DNA-aneuploidy mdi- cated the presence of DNA-biclonality that was also asso- ciated with resistance to chemotherapy.2' Surprising was the coexpression of both kappa and lambda light chains in the same DNA-aneuploid tumor cells in about 15% of patients, usually with IgG lambda isotype.58 The molecular basis of these aberrations from the current dogma of exclusive kappa or lambda light-chain expression and their association with gamma heavy chains remains to be clanified.59'#{176} Consistent with their major commitment to protein secretion, myeloma cells contain high levels of RNA, an average six times more than unstimulated lymphocytes.61'62 Exploiting the metachromatic properties of acnidine orange, cellular DNA and RNA content can be measured simulta- neously by two-parameter flow cytometry quantitating green (double-stranded DNA) and red fluorescence (single- stranded RNA).63 The detection of aneuploidy also in blood provided direct evidence for circulating tumor cells,25 long suspected on the basis of monoclonal idiotype-concordant blood lymphocytes" capable of plasma-cell differentiation in vitro.67 Thus disease progression and spread may occur by the hematogenous route, with specific tumor localization enforced by marrow-derived monocytes and I cells providing growth-stimulating factors.47'49'55 In addition to facilitating the quantitation of marrow plasmacytosis, flow cytometnic studies of nucleic acids have provided useful prognostic information.68 Thus no patient with DNA-hypodiploidy has ever responded to standard melphalan-prednisone or VAD; and higher response rates have been observed with increasing cellular RNA content. As with nuclear DNA, plasma-cell RNA index remained stable throughout a patient's disease and declined only rarely with relapse. Therefore the undoubted clonal evolution that produces drug resistance was not reflected in changes of cellular DNA and RNA content. Occasional mixed clinical responses to therapy could be traced to different DNA stemlines present in different disease sites. While the majority of tumor cells have plasma-cell fea- tunes, self-renewal must be sustained by stem cells earlier in the maturation sequence.67'69'7#{176}Several groups have searched for the expression of early B, I and myelomonocytic mark- ens.7'72 In almost 50% of patients, the pre-B antigen common acute lymphoblastic leukemia antigen (CALLA) was PLASMA CELL MYELOMA-INSIGHTS AND ADVANCES Table 2. Duff. rentiation Phenotype Calla + % Incidence 50 Myelomonocytic 13 T-antigen ? TCR-9amma rearranged LDH 40 50 and Lineage Infidelity Comment Coexpression with cIg and good prognosis Poor prognosis Poor prognosis when two myeloid markers present Coexpression with cIg and my- eloid markers No clinical correla- tion High levels in terminal disease phase with lym- phomalike features and poor prognosis Reference 72 73 74 74 102 1 14 expressed in a large fraction of tumor cells (Table 2).72 The coexpression of CALLA and monoclonal clg by the same aneuploid tumor cells unmasked a novel tumor-cell phenotype without known counterpart in normal B-cell differentia- tion (Fig 1). Such differentiation infidelity was also shared by the mature plasma-cell antigen Rl-3, which was jointly expressed with CALLA in about 40% of patients. The consistent presence, in all cases of DNA-aneuploid myeloma, of CALLA-positive cells with diploid DNA content (but 867 without clg expression) raised the possibility that diploid precursor cells generated the aneuploid plasma cells. Sub- populations of cells with CALLA/ cIg, CALLA/cIg, and CALLAjcIg may represent different maturation stages of plasma-cell myeloma. The authors have observed a more favorable clinical course in patients with CALLA expression, while others have concluded that this phenotype was harmful.73 Myelomonocytic antigen expression was reported recently in 1 3% of patients with myeloma (Table Those with dual myeloid antigen expression (M5 and MY7) also showed 1- and early B-cell features, high labeling index, and a poor prognosis. As expected from frequent elevations of serum beta-2-microglobulin (B2M) level, most patients showed tumor cell-surface expression of B2M.72 Both surface expres- sion and serum levels of B2M can be augmented after treatment with interferon-alpha, although correlations with clinical response have not been detected (Epstein J, Barlogie B, Alexanian R, unpublished observations, June 1988). Thus myeloma is a disease in which the majority of tumor cells are aneuploid with a differentiated B-cell phenotype but with subpopulations that also express early B, possibly 1, and even myelomonocytic features. The additional presence of diploid cells with an immature phenotype suggests that aneuploid myeloma originates from a stem cell with a different (ie, diploid) DNA complement.72 While differen- tiation and lineage infidelities may reflect merely malignan- cy-associated aberrations, they may indicate alternatively that transformation involved a plunipotent stem cell with a flexible pattern of gene expression. More specifically, the asynchrony of antigen expression in myeloma may reflect ``"T'' j- I I Fig 1 . Phenotypic hetero- geneity in a patient with hyperdiploid multiple myeloma. Hyperdi- ploid cells have high RNA content; react with anti-B2M, J5, and Ri -3 and show monoclonal clgA kappa expression. Diploid cells have low RNA content with- out monoclonal clg reactivity but express B2M and CALLA. Abscis- sa. DNA content; ordinate, fluo- rescence intensity of cellular fea- ture. o. CIgA B2 c DeA cea R1-3 CIgA 868 BARLOGIE ET AL Table 3. Factors Produced by Myeloma Cells Factor Comment Reference IL-i beta TNF-beta TNF-alpha BCGFII (IL-5) lL-6 B2M OAF, chromosome 2q; autocrine growth factor? OAF, chromosome 6p2 1 Autocrine growth factor in CLL, HCL; not evaluated in myeloma; on chromosome 6p2 1 Myeloma cell line (RPMI 8226)-autocrine growth factor (?); chromosome 5q23.3-q32 Myeloma cells and marrow-adherent cells Increased in most patients; poor prognosis with high serum levels; chromosome 1 5q2 1-q22 78 79 77 80 56 54 55 138-141 abortive differentiaton during an ordered rather than sto- chastic hematopoietic development with sequential commit- ment to megakaryocytic, erythroid, myeloid, and, finally, B-cell lineage.76 The demonstration of erythroid or mega- karyocytic antigens on myeloma cells would support such a model (Epstein J, Banlogie B, unpublished observations, December 1988). Consistent with the variety of disease features, myeloma cells produce many cytokines in addition to immunoglobu- lins. Osteoclast-activating factors have been identified as TNF-beta (lymphotoxin) and IL-l-beta (Table 3)77.79 While usually undetected in mature B cells, the continued expres- sion ofTNF-beta and IL-l-beta by myeloma cells78 suggests a role for those proteins in abnormal growth and differentia- tion, also invoked for IL-5 and IL-6.54 Indeed, TNF can act as a tumor growth factor and can promote cell proliferation in two other related B-cell malignancies, namely hairy cell and chronic lymphocytic leukemia.8#{176} Receptors for IL-5 (BCGF II) and IL-6 on myeloma cells may provide targets for therapy with immunotoxins or radioisotopes. Myeloma cells also express receptors for vitamin D3 , glucocorticoids, and sex hormones (estrogens and progestins; Table 4)#{149}81.84 Future studies should clarify the biological functions and implications of these receptors in the different B-cell tumors. In view of the clinical use of glucocorticoids85 and alpha- interferon,86 correlations of response with receptor expression are important.81'87 Immunodeficiency mainly of B-cell, and less profoundly and frequently of 1-cell, type is responsible for recurrent infections, usually of bacterial origin.88'89 In munine plasma- cytoma, B-cell suppression has been traced to a plasma-cell factor that causes monocytes and macrophages to produce a suppressor of normal B-cell proliferation#{176}; a similar factor has not yet been identified in humans. An alternative mecha- nism concerns the suppression of normal B cells by immuno- globulin-binding factor (IgBF), which may be identical to the Ig-Fc receptor shed by I cells.9' In the munine MOPC- 3 1 5 model, IgA-binding factor produced by IgA-induced I cells reacted with surface IgA on MOPC-3 1 5 cells; this resulted in the inhibition of both tumor growth and Ig production by the suppression of myc and Ig gene tran- scniption, respectively.92 The resistance to cytotoxic drugs poses a major obstacle to the successful management of myeloma and other neoplastic diseases. Refractoriness to multiple antitumor agents after exposure to one drug is referred to as MDR, a feature that eventually The MDR p-glycoprotein becomes dominant in cultured tumor cells.23'93 phenotype has been linked to the presence of a (pl7O) that functions as an effiux pump for certain anticancer agents, such as anthracyclines and ymca alkaloids.94'95 Using the MoAb, C219, which recognizes the cytoplasmic domain of p170,96 high levels of MDR expres- sion have been observed in myeloma cells and have been linked to clinical resistance to the VAD regimen.97 Such resistance has been overcome with the calcium channel blocker, verapamil,98 presumably by retaining higher cellular levels of adniamycinY The frequency and degree to which VAD resistance can be overcome with verapamil is now under study.'#{176}#{176} Molecular Genetics Studies of immunoglobulin gene rearrangement (as the molecular hallmark of a B-cell tumor) may explain the phenotypic heterogeneity and differentiation infidelity of myeloma.53 As expected, H rearrangement could be detected in proportion to the degree of marrow plasmacytosis. Multi- Receptor for BCGFII (lL-5) lL-6 Interferon-alpha Glucocorticoid Estrogen, progesteron Vit D3 Table 4. Receptors Expressed on Myeloma Cells Comment Cell lines, autocrine mechanism (?) Cell lines and fresh samples; me- diates autocrine or paracrine mechanism Active against low-mass disease; chromosome 2 1q2 1 Cell lines and fresh samples; correla- tion with clinical response to glu- cocorticoids not yet established; chromosome Sql i-q13 Biological effects (?); chromosome 6q24-q27 (ER) and 1 1q13 (PR) Mediates inhibition of proliferation and induction of new phenotypes by Vit D3 Reference 56 54 7 86 81 85 83 84 82 PLASMA CELL MYELOMA-INSIGHTS AND ADVANCES 869 pie rearranged bands were noted in only 5% of patients, indicating that clonal evolution was reflected rarely at the immunoglobulin gene level (Selvanayagam P. unpublished observations, September 1988). The concurrent rearrange- ment of Cu and JH genes in some patients resulted either from different tumor clones in different stages of B-cell maturation or from the coexpression of normally unasso- ciated phenotypes. The authors' finding of clg kappa coex- pression in IgG lambda myeloma was confirmed at the molecular level, with Ck rearrangement present in some patients with lambda light-chain production. Since early stem cells may be the source of myeloma, analysis was also carried out of 1-cell receptor genes, which are part of the immunoglobulin supergene family. Surpnis- ingly, 35% of patients showed 1cR-gamma rearrangement, while 1cR-beta and 1cR-alpha genes were not affected.'#{176}2 Identical frequencies of rearranged bands with 1cR-gamma and JH probes supported the neoplastic origin of 1cR-gamma rearrangement. In a survey of HLA-associated gene expression in human B-cell malignancies, invariant chain messenger RNA (In- mRNA) as well as HLA DR-alpha and HLA DR-beta-chain mRNA were expressed in all patients with either acute or chronic lymphocytic leukemia.'#{176}3 In contrast, only three of 1 5 patients with myeloma demonstrated In-mRNA expres- sion. Thus the In gene was expressed in neoplastic cells early in the maturation sequence, concurrent with the activation of other genes encoding histocompatibility class II antigens, and preceded the activation of immunoglobulin genes.'#{176} While advances in chromosomal banding and molecular techniques have clarified the role of cellular oncogenes in some B-cell lymphomas and leukemias, the difficulty in obtaining adequate metaphase chromosomes and the dearth of specific karyotypic aberrations have hindered similar progress in plasma cell myeloma. With the presumption of pre-B-cell involvement in human myeloma72 and the regular c-myc gene deregulation in murine plasmacytoma,'#{176}5"#{176} c-myc and other oncogenes implicated in malignant lym- phoma have been studied also in human myeloma (Table 5). High levels of c-myc RNA expression were observed in 25% of patients, without apparent abnormalities of myc RNA transcript size.'#{176}A7 s with t(8;14) chromosomal transloca- tions, myc gene activation was found more commonly in patients with IgA isotype but resulted only rarely from DNA rearrangement and was not associated with DNA amplifica- tion.'#{176A}8nalogous to recent observations in Burkitt's lym- phoma, Meltzer et aV#{17r6e}ported mutations in the 3' region of the first c-myc exon (Pvu II and Alu I endonuclease sites) in ten of 16 human myeloma samples and cell lines; we have not confirmed this observation. None of 60 patients with Table 5. One ogenes in Plasma -Cell Myeloma Abnormality Rearrangement Amplification Deletion High mRNA High protein expression expression c-myc 4/120 0/120 0/120 9/37 ND L-myc bcl-1 bcl-2 0/22 5/1 20 0/60 0/22 0/120 0/60 2/22 0/1 20 0/60 ND 0/40 0/40 ND ND ND. not done. c-H-ras 0/40 0/40 ND ND 17/23 myeloma showed rearrangement of bcl-2 (commonly involved in follicular lymphoma), consistent with the rarity of t(14;18) translocation in myeloma. Five of 120 patients had rearrangement of bcl-I but without corresponding mRNA elevation."0 Careful scrutiny of chromosomal breakpoints disclosed frequent involvement of the short arm of chromosomes 1 and 1 i,' where Kirsten-ras and Harvey-ras genes are located. Using pan-ras and H-ras antibodies with flow cytometry, 17 of 23 patients with active myeloma had high p2 1 expres- sion)" An inverse relationship between p21 levels and tnisomy 1 1 suggested that suppressor genes were present on chromosome 1 1.h12 The frequent elevation of p21 protein indicated that H-ras oncogene is involved in the pathophysi- ology of myeloma, as supported further by the shorter survival time of patients with high p21 levels." The mecha- nism of H-ras gene activation is currently under scrutiny, especially in regard to gene mutation as the commonest mechanism of nas gene activation in other human tumors. Biology Summary and Future Projections Cytogenetic and molecular data indicate the presence in myeloma of DNA rearrangements similar to those observed in malignant lymphoma. Such chromosomal translocations presumably result from recombination errors during immu- noglobulin gene rearrangement (ie, B-cell commitment) with activation ofjuxtaposed oncogenes."3 Phenotypic evidence of differentiation and even lineage infidelity, with coexpression on terminally differentiated B cells of early B,72 myeloid,74 and 1-cell markers74 may reflect abortive differentiation in the process of an ordered sequential rather than a stochastic lineage commitment, thus placing the oncogenic events in myeloma possibly to an early stage in hematopoiesis.76 Disease evolution has not been studied systematically. Preliminary data suggest disease dedifferentiation occasion- ally with cessation of myeloma protein secretion and produc- tion instead of high levels of serum lactic dehydrogenase (LDH) during the terminal phase of disease transforma- tion."4 Similarly, the development of acute myeloid leuke- mia in up to 25% of patients 10 years after diagnosis of multiple myeloma has occasionally been interpreted as a natural disease evolution rather than as a treatment-induced secondary malignancy,"5 thus supporting the notion of myeloma as a tumor arising early during hematopoietic differentiation (Fig 2). Sequential investigations during the disease course of individual patients are likely to reveal a progressive expan- sion of myeloma progenitor cells with higher proliferative activity and earlier phenotypic characteristics. Such infor- mation can then be used to probe for the presence of such features in rare cells earlier in the disease course. Studies of human plasma-cell lines suggest that BCGF II (IL-5) may be an autocrine growth factor in some patients with myeloma.56 Receptors for IL-6 (BSF-2) may mediate the biological activity of IL-6 produced mainly by bone marrow-derived monocytes (paracrine mechanism)55 and/or by the tumor cells themselves (autocrine mechanism).54 In view of the three-signal model advanced by Kishimoto"45 for 870 BARLOGIE ET AL Myeloma Cell Phenotype, Kinetics, and Drug Sensitivity S 8 g 55 55 Fig 2. Model of myeloma ontogeny. On the basis of available phenotype and molecular data (see text), a DNA-diploid myeloma stem cell early in hematopoiesis is postulated with sequential abortive commitment to megakaryopoiesis, erythropoiesis. granu- lopoiesis, and, finally. B-cell lineage. Terminally differentiated B cells (plasma cells) represent the dominant tumor phenotype, usually with DNA-aneuploidy and frequently asynchronous expression of earlier stages of differentiation. Proliferation is highest at an early commitment stage with greater sensitivity to melphalan. whereas plasma cells (producing a variety of cytokines) are kinetically inactive and highly sensitive to glucocorticoids. the activation, proliferation, and differentiation of normal B cells by IL-4, IL-S and IL-6, these lymphokines probably play an important role in sustaining the growth and differen- tiaton anomalies of human myeloma. For example, the production by tumor cells of IL-l,78'79 TNF,77'8#{176a}nd IL-4 or IL-556 may sustain both an autocnine growth-stimulatory loop and IL-6 production by bone marrow monocytes,55 promoting the differentiation of earlier B cells into plasma cells. Abnormal differentiation with lineage infidelity (pres- ence of myeloid and 1-cell markers on plasma cells) suggests that receptors for B-cell growth and differentiation signals may also be expressed aberrantly. Comprehensive studies, at the single-cell level, of cytokine production by tumor cells, lymphokine receptor expression, proliferative activity, hema- topoietic lineage, and phenotype stage are required to clarify these questions. Multiparameter flow cytometry81'87 and image analysis, together with in situ hybridization, are suitable research tools for such investigations. The key trigger to self-sustained and ultimately relent- lessly progressive plasma-cell accumulation is likely to result from the abnormal expression of normal cellular genes by a variety of possible mechanisms, such as gene rearrangement, mutation, and/or lack of suppressor gene activity due to deletion of critical "antioncogenes." ` 12 High myc expression, usually without DNA rearrangement, in about one quarter of patients suggests that point mutations may be the major cause, resulting in impaired nuclear protein binding to myc DNA sequences and consequently uncontrolled growth, as in Burkitt's 6 Mutational activation of H-ras unop- posed by controlling sequences on chromosome 1 1 may be an additional or separate mechanism of abnormal growth. ETIOLOGY In the mouse, an oil granuloma induces a preneoplastic chronic inflammation that progresses to plasmacytoma with myc gene deregulation'#{176}; in contrast, the etiology of human myeloma remains elusive. Several oncogenes (c-myc and H-ras) appear to be involved, but their link to the initiation and progression of myeloma is unclear. Radiation exposure, long known to induce myeloid leukemias and certain solid tumors, has sometimes led to myeloma 1 5 to 20 years h7121 Other epidemiologic surveys have demonstrated an association with benzene'22 and asbestos,'23 as well as with certain agricultural occupations.'24"25 Severe immunosup- pression with organ transplantation, while inducing B-cell lymphoma, has rarely led to plasma-cell myeloma.'26 Simi- larly, while B-cell lymphomas have been recognized as a manifestation of the acquired immunodeficiency syndrome (AIDS), associations between human immunodeficiency virus (HIV) infection and myeloma remain anecdotal.'27"28 Only about 10% of persons with benign monoclonal gammo- pathy (one of the few benign disorders with DNA- aneuploidy of plasma cells25) develop myeloma after at least 10 years of follow up.2 The persistence of a low-level mono- clonal protein after marrow-ablative chemoradiotherapy for myeloma in remission suggests that a benign gammopathy often precedes myeloma and is resistant to supralethal doses of therapy because of the low proliferative activity of BMG- associated plasma cells.'29 The presence of tumor cells in peripheral blood is relevant to an understanding of disease progression and has been suggested by several studies, including (1) isotype-con- cordant surface immunoglobulin expression by idiotypic lymphocytesTM'65; (2) differentiation of CALLA-bearing pen- pheral B cells to monotypic plasma cells in vitro63; (3) circulating DNA-aneuploid cells20; and (4) presence of immunoglobulin gene rearrangement in blood.66 Werne et 30 examined the ratio of kappa- and lambda-positive lymphocytes in blood and noted the phenomenon of light- chain isotype suppression in stable phases of disease, con- trasting with isotype predominance during disease pro- gnession. DIAGNOSIS AND STAGING Solitary and Indolent Myeloma Solitary plasmacytoma of bone or soft tissue,'3' indolent on smoldering myeloma,3'4"32 and symptomatic generalized 33 represent distinct clinical phases in the spectrum of plasma-cell myeloma (Table 6). The occurrence by chance of a painful pathologic fracture from a single tumor mass apparently allows the recognition of this disease about 5 years earlier than otherwise possible. Provided strict criteria for staging are applied, local radiotherapy appears to be curative in about one half of the patients. Staging criteria include no signs elsewhere of monoclonal plasmacytosis (best by DNA-clg flow cytometry), lack of other bone lesions or abnormalities on sensitive radiographic examinations (com- putenized axial tomography [CAT] and nuclear magnetic resonance), and preservation of normal immunoglobulin PLASMA CELL MYELOMA-INSIGHTS AND ADVANCES levels. Less rigorous criteria probably explain the divergent conclusions reached in regard to the natural history of this entity. Following radiotherapy, abnormal globulin levels are usually reduced markedly, indicating that the localized disease was encompassed by the radiation field. However, low monoclonal protein levels may persist indefinitely in some patients, indicating residual plasma cells that remain dormant in a manner analogous to BMG. Some localized plasmacytomas are radioresistant (eg, those with DNA- hypodiploidy or with low RNA content), portending resis- tance to later chemotherapy and a poor prognosis.68 The curability of localized plasmacytoma in a substantial propor- tion of patients indicates that myeloma arises from a single focus; the persistence of monoclonal gammopathy without later evolution of generalized disease suggests that BMG is a preneoplastic entity, requiring additional factors to progress to myeloma. A similar explanation may pertain to the persistence of low levels of abnormal globulin after high-dose consolidation therapy for responsive multiple myeloma.'29 When a solitary lesion is not associated with bone destruc- tion (ie, perhaps because IL-l or TNF-beta production is low), generalized myeloma may develop and progress slowly without symptoms. Only a chance electrophoresis leads to the diagnosis of such indolent or smoldering disease. Similar to patients with early phases of CLL or nodular lymphoma, chemotherapy is unnecessary until morbidity occurs or becomes imminent (ie, myeloma protein >5 g/dL or new bone lesions). The similar prognosis of patients treated many months after diagnosis to that of the usual patient treated promptly indicates that drug-resistant tumor cells have not expanded. A low plasma-cell labeling index can predict an indolent disease course in asymptomatic patients,30'31'32 many of whom live longer than 10 years after diagnosis.6"32 Clinical Staging ofSymptomatic Myeloma Different centers have defined the extent of myeloma from variations of a schema that considers the degree of anemia, hypercalcemia, and other disease features.'33"34 Based onigi- nally on a system devised from direct measurements of total myeloma mass,'35 increasing tumor burden has been asso- ciated with shorter survival time.'36 Although the application of different criteria for staging by different centers has prevented a meaningful comparison of treatments between groups, the consistent use within a center or group has allowed more reliable comparisons of new treatments with historical treatments. Recent studies have improved further the reliability of staging systems. Thus the serum level of beta-2-micnoglobu- lin (B2M), by reflecting both tumor mass and renal function, offers a single measurement that provides as clear a separa- tion of risk groups as any staging system.'38"4' Among 100 previously untreated patients, the authors found progressive shortening of survival time for patients with increasing B2M levels.'42 Other studies have revealed that the extent of bone lesions is an unreliable index of tumor load, that renal failure occurs much more often with advanced disease, and that the extent, morphology, and DNA/RNA content of marrow plasma cells are important factors. For example, the shorter 871 Ta ble 6. Diagnosis and Staging Diagnosis MGUS Indolent myeloma Overt myeloma Differentiating Parameters Normal bones, Hb, Ca, Ig; Marrow plasmacytosis <10% Labeling index < 1% Few lytic bone lesions without fractures Normal Hb, Ca, Ig; Marrow plasmacytosis <20% Labeling index <1% B2M <4. 4-6, >6 mg/L Dune-Salmon Staging System Marrow plasmacytosis <20, 20-40, >40% survival of patients with plasmablastic myeloma may be related to higher proliferative activity,30 confirmed in several clinical trials to shorten survival independent of tumor ma5534,35'43 or B2M levels.'44 In studies evaluating the role of high-dose alkylating agent therapy for VAD-refractory myeloma, the authors observed high-serum LDH levels of >300 U/L prior to or within 2 weeks after therapy in about one half of patients."4 High LDH conferred a rapidly progressive course with lympho- malike clinical features, in a manner similar to that seen in patients with the blast phase of chronic myelocytic leukemia or with transformed lymphoma. Thus high LDH seems to define a high-grade myeloma as a result ofclonal evolution to a more undifferentiated tumor-cell phenotype and/on by progressive expansion of drug-resistant tumor cells. ` ` Quan- titative studies of tumor-cell LDH content should distinguish these alternatives (Van NT, Epstein J, Barlogie B, unpub- lished observations, December 1988). Preliminary data in 100 previously untreated patients also showed that high LDH levels occurred more frequently with renal failure and portended a poor prognosis.'42 Thus there are now a variety of quantitative and tumor cell-derived parameters that correlate with prognosis (Table 7). From a large retrospective analysis of previously untreated patients who received similar chemotherapy, the dominant variables associated with distinct clinical points were determined, eg, (1 ) absolute resistance endwith DNA hypodipoloidy and lower remission rates with low plasma-cell RNA index and high B2M serum levels; (2) shorter remissions with high serum-LDH and low plasma- cell RNA index; and (3) short survival in patients with high serum-LDH and B2M levels (Table 8). The importance of similar and mainly tumor-intrinsic parameters for both remission induction and long-term prognosis emphasizes the dominant role of marked cytoreduction from initial therapy in each patient's ultimate outcome. The authors envision that, as in the leukemias and lympho- mas, cytogenetic and molecular disease entities will eventu- ally be defined that are associated with unique clinical presentations and prognosis. Meanwhile, relationships among the recognized prognostic factors should be clarified, so that the adverse effects of high LDH,"4 low CALLA expression,72 high H-nas activity,' ` ` myelomonocytic pheno- type,74 and high proliferative activity' can be traced to few critical biological features to be exploited therapeutically. 872 Table 7. Prognostic Factors in Myeloma Endpoint Adverse Pretreatment Variable Reference Response Time to relapse Survival time -DNA -Low hypodiploidy RNA index -High tumor mass -High B2M . . . MDR expression -Low RNA index -High B2M -High tumor mass -High LDH -High B2M -High tumor mass -High LDH -High labeling index . . . Low RNA index . . . DNA hypodiploidy . . . CALLA-negative . . . Butyrate esterase- positive . . . H-ras expressed 68 68 68 142 97. 100 142 138- 143 1 36 and many others 114 34, 35, 144 68 68 72 74 111 - , established; . . . . suggested. OBJECTIVES OF THERAPY The degree of cytoreduction achieved in most responsive patients rarely exceeds 99%#{149}I45With most available treat- ments, disappearance of myeloma protein is evident in only about 10% of those with IgG or IgA peaks, but is evident in about 60% of those with only Bence Jones protein, so that the overall frequency of "complete remission" is about 20%. Rigid criteria for disappearance of abnormal protein should include immunoelectrophoresis and immunofixation tech- niques. Most centers define a response either as a 50% reduction in myeloma protein concentration' or as a 75% reduction in M-protein synthesis'4"48 with disappearance of Bence Jones protein (as in this review). The speed of cytore- duction, calculated from changes in IgG or IgA myeloma protein, varies with different treatments. Thus in responding patients, the median time required for a 50% reduction in IgG or IgA myeloma protein was much shorter with primary VAD (0.4 months) or VCAD-VAD (0.9 months), than with VCAP using bolus vincnistine-adniamycin (1 .2 months) or standard melphalan-prednisone (2.2 months). High-dose melphalan with total body irradiation achieved the most rapid cytoreduction with protein levels declining in accon- dance with their expected plasma clearance. The remission time of responding patients with multiple Table 8. Multivariate Analysis of Prognostic Factors Among 100 Patients Treated at MD Anderson Cancer Center Endpoint Response Relapse-free survival Survival Adverse Variable In Order of Entry Low RNA (<4) High B2M (>6 mg/L) LDH (>200 U/L) RNA(<4) High LDH (>200 U/L) High Mass (Dune-Salmon) High B2M (>6 mg/L) P .001 .001 .05 .06 .001 .09 .10 BARLOGIE ET AL myeloma has been overlooked as an important endpoint. Few published reports have included this feature in the compani- son of different treatments. Now that effective treatment alternatives for remission induction and consolidation are available, remission time assumes more importance in com- paring treatments. Disease relapse may be detected early in most patients from rising myeloma protein levels. The median tumor-doubling time for patients with IgG on IgA myeloma protein is about 2 months, with more rapid relapse in those who responded rapidly. In recent years, and espe- cially after VAD, more patients have been recognized with "phenotypic escape."49 Most commonly this is manifested by increasing bone marrow infiltration with progressive anemia, bone destruction, hypercalcemia, and rising B2M and LDH levels, despite low or even absent levels of myeloma protein. Transformation to a more aggressive malignancy with rising LDH has been associated with disease in lymph nodes, liver, brain, or blood."4 Whether such patients are more likely to develop karyotypic or phenotypic changes from those present at diagnosis is not clear. The role of new therapies, such as VAD and/or high-dose melphalan, in causing such changes or allowing them to become manifest because of survival prolongation needs to be assessed. TREATMENT For the past 25 years, intermittent melphalan-prednisone (MP) has been the therapy ofchoice for multiple myeloma in community practice. Extensive clinical trials with other drug combinations have not shown a major improvement in dis- ease course.'50"5' Since the details of numerous clinical trials have been summarized elsewhere,'2"3 this review will focus on those studies promising substantial future gain. Since these treatments were developed first for refractory disease, effective salvage regimens will be reviewed prior to discuss- ing their role as initial therapy. Effective Salvage Regimens VAD and dexamethasone. Not until the introduction of VAD (combining pulses ofhigh doses ofdexamethasone with continuous infusions of vincnistine and adniamycin) were there frequent, marked, and durable tumor cytoneductions in patients resistant to standard therapies.'52 Dexamethasone alone was also effective,85 but VAD induced more frequent remissions in patients with relapsing disease or with primary drug resistance of less than 1 year duration, provided favor- able DNA/RNA features of plasma cells were present (Table 9). A longer duration of primary resistance was associated with DNA-hypodiploidy or low plasma-cell RNA index in nearly one half of the patients, providing one biochemical explanation for such resistance. The greaten efficacy of VAD than dexamethasone among relapsing patients was attributed to the greaten sensitivity of proliferat- ing tumor cells to the cycle-active drugs vincnistine and adriamycin. Identical to studies in newly diagnosed patients, a high serum B2M level (> 6 mg/L) was the dominant adverse feature for survival time.'52 High-dose melphalan and total body irradiation with bone marrow transplantation. To date, 65 patients with PLASMA CELL MYELOMA-INSIGHTS AND ADVANCES Table 9. Response to Salvage Treatment DEX VAD HDM<9Omg/m2 HDM9O-i4omg/m2 HDM 140 mg/rn2 + TBI Not hypodiploid and RNA inde x 4. Treatment Related Resistant to MP MP MPandVAD MPandVAD MP and VAD to Dur ation of Primary Resistance and to DNA-RNA Fe atures % Responding (No. Treated) Unresponsive for 12 months + Favorable DNA/RNA Other 32(28) 56(32) 67(12) 47(i5) 77 (13) 17(18) 14(14) 0(8) 53(15) 100(2) 873 VAD-nefractory myeloma have been treated with high dose melphalan (HDM), either alone'53"54 or with total body irradiation8 (TB!; 850 cGy in five fractions 1 2 hours apart) and supported with autologous bone marrow. The latter was harvested, whenever possible, during an earlier remission phase and contained less than 30% plasma cells. The ration- ale for autologous marrow transplantation in this marrow- derived malignancy was based on the predominantly termi- nal B-cell phenotype with a small proportion of clonogenic tumor cells capable of self-renewal.42 With the addition of TBI, virtually all patients responded (Table 9), and although the patients were selected more carefully, the median remis- sion and survival times were longer than with the melphalan alone (Table 10). The previous adverse influence of a long duration of primary drug resistance (> 12 months) and of certain DNA/ RNA features was no longer observed when high melphalan doses (ie, >90 mg/m2) were employed, indicating both the lack of cross-resistance to VAD and, more importantly, entirely different mechanisms ofdrug action (Table 9). With better patient performance (Zubrod <2) and normal renal function, early mortality was virtually eliminated. The long- est remission and survival times were observed among patients whose LDH levels were less than 300 U/L both prior to and during the first 2 weeks after therapy (Table 10 and Fig 3)l7 The short survival times in patients with higher LDH levels were due to rapid recurrence of a high-grade myeloma with lymphomalike features. Among patients receiving bone marrow autografts, neither the extent of plasmacytosis nor the tumor-mass kinetics at the time of marrow harvest influenced remission and survival durations. Since complete remissions with current marrow-ablative regimens occurred rarely and since the phenotype of the myeloma stem cell was unknown, autologous bone marrow purging by immunologic means appears unwarranted. Instead, therapeutic research should focus on the develop- ment of regimens that provide even greater cytoreduction. Potential alternatives to marrow autografts include hemato- poietic growth factors'55 and/or autologous blood stem cells,'56"57 particularly in patients with extensive marrow plasmacytosis. The combined use of hematopoietic growth factors and autologous stem cells may reduce the duration of severe neutropenia and hence the risk of sepsis with ablative treatments. Allogeneic bone marrow transplanation. Because of the higher mortality from graft-v-host disease (GVHD) among older patients, the use of allogeneic bone marrow transplan- tation (BMT) has not been explored systematically. Cyclo- No TBI + TBI N Ded 6 2 C LOH. Low-Low , `.5 5*#{216}4,1j C 0 0 0. 0 0. 0 8 16 24 32 40 0 8 16 24 32 40 Months Alter Treatment Fig 3. Survival of VAD-refractory myeloma after treatment with HDM with or without TBI (for details, see text). Longest disease control and survival were achieved in patients whose serum LDH levels did not exceed 300 U/L within 2 weeks of therapy. whereas patients with higher levels rarely derived clinical benefit. The prognostic Importance of LDH applied whether or not TBI was added. Table 1 0. Prognostic Factors with HDM fo r VAD-Refr % TBI N Response No 36 Yes 16 46 80 Median RelapseFree Survival (months) LDH, Low-Low 7 18 Othert 3 6 P .04 .03 P .04 .06 .006 LDH. Low-Low: LDH <300 U/L for at least 14 days after treatment. tOe: LDH 300 U/L before or within 14 days after treatment. actory Myeloma Mec8an Survival (months) LDH, Low-Low 10 35+ .18 Other 4 8 .19 P .009 .07 874 BARLOGIE ET AL phosphamide plus TBI and modifications, with syngeneic or allogeneic BMT, has reduced tumor mass markedly in about one dozen patients, many being treated during a partial remission.'58"6' Monoclonal protein persisted in many patients with progressive or unresponsive myeloma. In a recent European trial, about one half of the patients achieved complete remission, and few patients developed severe GVHD.'62 With the efficacy ofanti-CD5 MoAb in glucocor- ticoid-resistant GVH D, allogeneic marrow transplantation may be better tolerated by older patients.'63 A comparison of autologous with allogeneic BMT (in patients with compara- ble disease features who received identical cytoreductive therapy) may clarify the possibly adverse effect of autolo- gous tumor-cell reinfusion and the potential gain from a graft-v-myeloma effect. Primary Therapy VCAD-VAD. Because of its superior activity in melpha- lan-refractory disease, the VAD regimen has been assessed in previously untreated patients. We have not seen any major gain in survival with VAD or VCAD-VAD that includes oral cyclophosphamide (VCAD) in comparison with preceding regimens, so that no improvement in the frequency of complete remission on survival time has resulted after a I 5-year experience with many drug combinations.'42 The lack of survival prolongation with a regimen that was superior for resistant disease is puzzling, particularly since tumor halving times have shontened progressively from a median of 2.2 months with MP to I .2 months with VCAP and to 0.4 months with VAD. The authors reason that different tumor cells may be affected by the different treat- ments. VAD with high-dose glucocorticoid may reduce pre- ferentially more differentiated tumor cells so that such manifestations as myeloma protein production, anemia, and hypercalcemia are controlled rapidly. This effect contrasts with standard MP, which may be more effective against myeloma precursors, so that slower but equally sustained tumor control is achieved (Fig 2). Interferon. Interferon-alpha is an active cytoreductive agent for many patients with low tumor load both at diagnosis and during first remission.S6M6S The combination of interferon with VBMCP as initial therapy achieved a higher frequency of complete remission than seen previous- ly.' However, interferon rarely benefits patients with resis- tant or relapsing disease several years after diagnosis. An attractive biological feature of interferon concerns the fre- quent recovery of normal immunoglobulins in many responding patients, an uncommon event with standard chemotherapy. ` HDM TB!. The Medical Research Council reported that high-dose intravenous (IV) melphalan produced a 78% response rate (with 27% complete remissions) in 4 1 newly diagnosed patients with advanced disse.'67'68 A subsequent regimen included initial VAMP (vincnistine-adriamycin by continuous infusion plus methylprednisone instead of dexa- methasone in VAD) followed, at maximum cytoreduction, by HDM (200 mg/m2) with autologous remission marrow. Preliminary data indicated a complete remission rate of 30%, with an additional 50% of patients who achieved partial responses; 10% suffered early mortality.'69 The authors are conducting similar studies in newly diag- nosed patients, in which VAD is prescribed for those with intermediate or high tumor mass; responding patients then receive HDM (140 mg/m2) and TB! (total dose of 850 cGy in five fractions) supported by autologous remission marrow. Only one of five patients treated to date has achieved a complete remission. Problems and Promises of Therapy Combinations of alkylating agents with or without adnia- mycin have not proven superior to standard MP introduced about 25 years ago. During the past 5 years three effective treatments have been discovered: (1 ) alpha-interferon for low tumor-mass disease; (2) high-dose glucocorticoid thera- py85 with further benefit from continuous-infusion vincnis- tine-adriamycin in proliferating myeloma'52; (3) HDM with superior antitumor effect from added TBI.8"29 The infrequency of complete remissions after marrow- ablative therapies with autologous BMT seems unlikely to be due to tumor-cell reinfusion. This reasoning is based on the slight further reduction of residual myeloma protein in responding patients consolidated during remission and the low number of reinfused plasma cells in proportion to the number persisting in vivo. Furthermore, the infusion of autologous marrow with obvious plasmacytosis has not short- ened the duration of remission in patients with refractory myeloma. The "plateau phase" of myeloma during remission may represent a cytokinetic sanctuary this is resistant to high-dose therapy.'7#{176} Alternatively, a BMG-like condition with resistant and long-lived plasma cells may be a common precursor phase of myeloma remaining after successful enadication ofthe neoplastic tumor-cell population.'29 In addition, one must consider the persistence of causal agents and mechanisms sustaining the monoclonal gammopathy. Thus the continued production of a monoclonal protein after marrow-ablative therapy is not incompatible with durable disease control. SUMMARY AND CONCLUSIONS Plasma cell myeloma is a more complex neoplasm than suggested by the relative uniformity of its dominant plasma cells, which represent the terminal stage of normal B-cell differentiation. Phenotypic, molecular, and cellular genetic data favor the presence of a myeloma stem cell early in hematopoietic development so that, as in chronic myelogenous leukemia (CML), a far distance exists between the primordial malignant cell that was the target of malig- nant transformation and the dominant clinical phenotype. Traces of pre-B, myeloid, and I cells are coexpressed with the mature B-cell phenotype, an occurrence unknown in normal B-cell differentiation. Analogous to CML, disease progression is marked by disease dedifferentiation, occasionally with cessation of myeloma protein production and development instead of extnamedullary lymphomalike features with high LDH or PLASMA CELL MYELOMA-INSIGHTS AND ADVANCES 875 myelodysplasia/acute myelogenous leukemia (AML) syn- dnomes. The prognostic importance of serum LDH levels even in newly diagnosed myeloma suggests the early pres- ence of tumor cells with "LDH phenotype," which, as a result of drug resistance and proliferative advantage, expand preferentially during disease progression. Further character- ization of these cells may provide important clues about the ontogeny of multiple myeloma. Myeloma cells express many receptors logical signals that might be exploitable for different for therapy biowith immunotoxins or radioisotopes. Plasma cells and their pne- cursors also produce a variety of cytokines, some of which have putatively autostimulatory functions (eg, IL-l, IL-5, IL-6) and/on are related to disease manifestations (eg, IL-i and TNF-beta as OAF). The wealth ofcellular expression by plasma cells provides clues for understanding the mecha- nisms of gene activation and the nature of abnormal gnowth and differentiation. The accuracy of prognostically relevant staging systems has been refined with the use of new quantitative parameters that reflect tumor mass (ie, serum B2M levels) and biology. Further studies of cellular and molecular biology (ie, CAL- LA, H-ras) may reveal those tumor cell features that define clinical entities, response to therapy, and long-term pnogno- sis. The lack of a major advance in prognosis despite the use of more drugs and more intensive regimens justifies the con- tinued use of standard melphalan-prednisone for patients with a highly favorable prognosis, for the very aged, and for those with a short life expectancy due to other major medical problems.'7' However, a radical departure from standard practice is required to improve the prognosis for younger patients with poor risk features. Especially rational is the application, soon after diagnosis, of three active treatments that lack cross-resistance, namely, alpha-interferon, VAD, and HDM. Exploiting supportive care measures with mar- row or blood stem-cell support and/or with hematopoietic growth factors, one should seek a marked tumor reduction with ablative treatments to achieve durable remissions in most patients. As GVHD becomes more preventable and manageable, allogeneic BMT will become more feasible, and with comparative trials, the risk of autologous tumor-cell reinfusion can be assessed. The recent notion of an autocnine growth mechanism, as in acute myeloid leukemia,'72 suggests that future therapy can be designed to interfere more specifi- cally with the abnonmal expression of cellular genes, such as H-ras and c-myc. ACKNOWLEDGMENT The authors wish to express their appreciation to Mattie Thomas and Eva Menefee for their secretarial assistance. Scott- REFERENCES 1. Bataille R: Localized plasmacytomas, in Salmon SE (ed): Clinics in Hematology. Philadelphia, Saunders, 1982, p 113 2. 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