Document b5QZwwKwEqapar47MaNrrQ1zO

. -T 41* THE LAN AUGUST 25, 1973 ISBESTOS AND LARYNGEAL CARCINOMA KM. Stox .T. McGill Tr, Non, and Throat Infirmary, Uotrpool LI 7DP _ One hundred male patients with ummery ,qUarnout carcinoma of the larynx and one hundred matched controls with various non* malignant diseases were questioned about their expo sure to asbestos. Thirty-one patients and three con trols had experienced an important degree of exposure to asbestos. The difference between the two groups was statistically highly significant. The average latent interval between first exposure and development of laryngeal carcinoma was 30 years, and the average duration of exposure was 27 years. Introduction Pulmonary asbestosis is a recognised occupational hazard of long exposure to asbestos dust. There is now also considerable evidence to support the con tention that pulmonary asbestosis plays a definite role in the development of bronchial carcinoma,' and, furthermore, the association between mesothelioma of the pleural and peritoneal cavity and exposure to asbestos is widely accepted.** The results of a previous study of the relation between exposure to asbestos and cancer of the upper respiratory tract* indicated that exposure to asbestos was most likely to be of importance jn laryngeal carci noma. The present study is an effort to investigate in greater depth the Importance of asbestos in laryn geal carcinoma. Patients and Methods One hundred consecutive male patients with laryngeal carcinoma attending the Liverpool Ear, Nose, and Throat Hospital formed the bails of the study. The controls were a series of one hundred male patients, matched for age, who were attending the hospital for various non-malignant conditions. Doth groups were questioned to determine their exposure to asbestos and their smoking-habits. This in formation was obtained In both groups by personal inter view. All the tumours were histologically proven squamous carcinoma. The age-distribution of the patients and controls is shown in table I, and their smokbtg-hablu are shown in table il { , Results Out of one hundred patients with laryngeal cardnoma, thirty-one (31%) had important exposure to asbestos, as compared with three (3%) of the control T*1U l--AOX-DimtlSimON U* PATIENTS AND CONTROU Patient! A*e-*roup 41-50 51-60 61-70 71-00 11-40 Hittory of exposure No. % 4 IS 1) 42 10 >1 4 11 No history of exposure Na. % f 11 14 2S 46 u Ii Total 13 53 45 13 1 Controh tj 32 45 12 series. The difference between the two groups is statistically highly aignifiesnt 0c*=30 I, n=l, P< 0001). There were three types of occupational exposure: lagging of heating equipment (nineteen patients), scaling of boilers (three patients), and unloading raw asbestos on the docks (nine patients) (before the intro duction of container traffic). Analysis of data from these asbestos workers showed that the latent period between first exposure and the development of laryngeal carcinoma ranged from I to 54 years, the average being 30 years; the average duration of exposure was 27 years (table in). In those TASLS II--IMOKINO-HABtTJ Of PATIENTS AND CONTROLS Palirots -- History of. No history Controls exposure of exposure C%) No. % No. % Non-cmokcn 1-10 cigv./4*y 11-20 cip./fiy Over 20 dp./diy Pipe 4 !3 4 5 7 23 13 19 11 35 27 39 9 29 16 26 7 10 20 22 32 19 7 TAILS III--LATENT PERIOD AND DURATION OP EXPOSURE TO ASBESTOS ' . IN PATIENTS WITH LARYNGEAL CARCINOMA Yean 0-5 6-10 11-15 16-20 31-25 26-30 31-35 34-40 41-45 44-50 51-54 Letent period of txponirt 2 0 l 2 3 6 4 2 10 0 i Duration of exposure 4 4 2 0 2 S 2 10 0 1 i cases of laryngeal carcinoma associated with asbestos, \ the maximum incidence was in the 51-40 age-group, j as compared to the usual maximum incidence in the 61-70 age-group.* There was no difference in the smoking-habits of the patients who were asbestos workers compared to those patients who had no association with asbestos (table II). But, as might be expected, there was a \ greater percentage of non-smokers among the controls 1 compared with those patients who had laryngeal / carcinoma.* Discussion Whilst the results quoted above suggest that there is an assodation between exposure to asbestos and laryngeal carcinoma, it has to be admitted that this conclusion is based on a retrospective study, with ail `the disadvantages of such a study. A prospective study of the -would be difficult, however, since th/annual incitjcnccW laryngeal carcinoma i of the order of l/J0,005, td if wuulli be difficult to collect Vsatatic populatiqpr of asbestos workers large enough to pro3CHrnifl5aent cases of laryngeal card- noma for a prospective survey. In our series of thirty-one cases of laryngeal carci- , l | 1 l I Ii ASARCO ALV 0002058 TOT LjUXIT, AUGUST 25, 1973 417 noma with a history of exposure to asbestos there was only one patient with pulmonary asbestosis. (There vis apical pulmonary fibrosis in five other cases, but (his is unlikely to be related to asbestos exposure.) The explanation of this apparent anomaly seems to be that heavy industrial exposure in the past has in most cases resulted in severe asbestosis and early death before the patient could survive long enough for cancer to develop. With the introduction of modern precautions for the protection of asbestos workers, there has been a fall in the incidence of asbestosis and an increase in the number of cases of asbestos-associated cancer.* This would be in keeping with a long latent period, of say 30 years, as in. our patients. x The patients' smoking-habits were similar, irrespec tive of their exposure to asbestos. As expected, how ever, there were more smokers among the patients than among the controls.* It may be that smoking is a cofactor in the development of laryngeal carci noma, but, as previously pointed out,* it is unlikely to be very important, since the incidence of larynceal carcinoma in the twentieth century has declined, slightly in the face of an enormous increase in tobacco' consumption. / We intend to perform histological examinations for asbestos bodies in patients with laryngeal carcinoma. Unfortunately, however, not many specimens are available because the vast majority of patients with laryngeal carcinoma are treated by radiotherapy. Even if the tumour recurs and the larynx becomes avail able for study after laryngectomy, it is doubtful whether asbestos bodies could be found--presumably they would lie at the centre of the tumour and thus be sloughed off as the tumour ulcerated during its growth. Even if they survived this insult, they would almost certainly slough out in the healing process after radiotherapy. As a pilot study, we examined serial sections from one larynx, but no asbestos bodies were found. Request, for reprints should be addressed to P. M. S. REFERENCES ]. Buchanan, W. D. Ann. N.Y. Acad. Sci. 1965, 132, 507. 2. Warner, J. C., Sleggi, C. A., Marchind, P. Br.J. ind. Mtd. I960, 17, 260. 3. Whitwcll, F., Rawcliffe, R. M. Thorax, 1971, 2, 6. 4. Siell, P. M., McGill, T. Lanttt, 1973, i, 67$. 5. Stdl, P. M. ibid. 1972, i, 617. 6. SclikofT, 1. T., Hammond, I. C. Churg, J.J. Am.mud. Ait. 1968, 204, 106. Hypothesis ACUPUNCTURE ANAESTHESIA G. M. Bull Medical Research Council Clinical Research Centre, Watford Road, Harrow, Middlesex HAI 3UJ _ ^ A possible mechanism to explain ry acupuncture anaesthesia is presented which takes into consideration the fact that acu puncture needles have to be vibrated or rotated and which is not invalidated by the lack of correlation between the traditional acupuncture sites and the anatomy of the peripheral nervous system. It is suggested that rhythmic stimulation causes areas of the cerebral cortex to become " locked on " to the stimulating rhythm and thus "busy" and unable to react to stimuli in the normal way. Two hypotheses are currently favoured to explain how acupuncture might induct anesthesia.' The one is hypnotism and the other is the so-called " gate hypothesis " of Mclzack and Wall.* The latter is based on postulated interactions at cord level between pain srimuli travelling in the A and C fibres of the peripheral nerves resulting from the differences in speed of transmission in the two classes of fibre. Neither of these accounts for the fact that it appears to be necessary for the act puncture needles to be vibrated or rotated either manually or electri cally.' A further hypothesis is presented below which takes this into account. It is known that some patients suffering from Jacksonian epilepsy whose attacks sun in a periphery can abort their atucks if they apply a strong stimulus to the limb proximally in the " path " of the ascending sensory or motor disturbance.*'* It is postulated that this stimulus causes the cortex in the area surround ing the dysrhythmic focus to become sufficiently refractory to block the spread of the dysrhythmia to the rest of the cortex. The " busy " area of the cor tex is partly refractory to further stimulation. There is another circumstance in which the cortex can be made refractory to random impulses, and that is when a rhythmic stimulus is fed in through a sensory channel. This is most easily demonstrated in the case of the visual cortex, where photic stimula tion at appropriate rates may induce a wide variety of subjective experiences not only in the visual fields but also in other sensory modalities. In many sub jects fits of varying sorts may be induced and demonstrated electrocncephalographically or seen clinically. This forms the basis of the use of photic stimulation in diagnostic electroencephalography. The phenomenon is not confined to the visual pathways, and similar effects can be demonstrated electroencephographically and occasionally clinically with rhythmic stimulation of the periphery or of the auditory pathways. The rate of stimulation appears to be critical and to vary between about 1 and 25 cycles per second. Moreover, the interval between volleys of stimulation appears to be impor tant in determining the response. Voluntary inhibi tion or augmentation of the responses can be demonstrated both electrocncephalographically and subjectively.'-' It appears that, when a sensory stimulus recurs at an appropriate frequency, large areas of the cortex may become F locked on " to that frequency or a harmonic of it and that its normal function may be thereby disturbed. The analogy with acupuncture anxsthesia is close. The frequency of vibration or rotation of the acupuncture needles is within the appropriate range I ASARCO ALV 0002059