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-1988 Elsevier Science Publishers B.V' (Biomedical Division) Smokiny and healih 1987: M. Aoki et a!. editors Na,r{ C E 'tttt5 m3teriat may be pcetected' hy copyright faw (Title 17 U.S. G,ode). 279 pASShttE SMpRING IS A RISK FACI'OR FOR LUNG CANCER IN NEVER SFlD1CI>w]G WO!!HN IN fiONG IIONG TAI HING LAM, RAR 1CEUNG CHENG Department of Cornrnunity Medicine, University of Hong Kong, Li Shu Fan Building, 5 Sassoon Road, Hong Kong. INTRCDiJCf ION In Hong Kong, lung cancer is the leading cause of death due to malignant neoplasms in both sexes. On a world scale, lung cancer death rates among men are not particularly high in Hong Kong. However, the rates in women are among the highest in the world, Four case control studies have been carried out in Hong Kong to investigate the ri'sk factors for lung cancer in wotoen, particularly smoking and passive smoking. They are reviewed as follows: I. 1976-1977 STUDY The first major study on risk factors for lung cancer was a case control study on 208 male and 189 female patients. The controls were 204 male and 189 female hospital orthopaedic patients. Smoking was found to be a major risk factor in males with a relative risk (RR) of 27.51. In females, the RR for smoking was only 3.48. 44.4% of the cases were non-smokers whose tumours were predominantly adenocazcihomas (45.2t )~.1 The role of passive smoking was studied by simply asking the question of 'Are you exposed to the tobacco smoke of others at home or at work?• For non-snoking women, 40.5% of the cases and 47.5% of the controls had passive smoking. The RR for passive smoking was 0.75 (p-0.38).2 II. 1981-1983 STUDY In the second cast control study, 200 female cases and 200 district female controls matched for age were interviewed in depth using a semi- structured questionnaire. The RR for ever smoking was 2.77. 44.01 of the cases had never smoked. Among the never-smoked wives, 61.4% of the cases and 51.8% of the controls had smoking husband. The RR for passive smoking due to smoking husband was 1.48 (P_0.16).3 III. 1981-1984 STUDY The third case control study included 163 female cases and 185 female controls from hospital orthopaedic patients. Unlike the pcevious two studies, only histologiCally and/or cytologically confirmed cases were included. A standardized questionnaire was used for interviewing. The AR for smoking was 4.12. The proportion of cases who were non-smokers was 46. 9%. The role of passive smoking was studied only on the adenocarcinoma Cases. For non-smoking wostrn, 61.7% of the adenocarcinoma cases and

280 44.4% of the controls had passive smoking due to smoking husband. T'be - ~RR for passive smoking was 2.81 (P<I.05), Analysis was also carried out by the site of the tumour. For centrally sited tumour, the RR for passive smokinj was 1.61 (P>0.05). For peri'pheral tumour, the RR was 1' 2.64 (P<0.05) ~, ~ IV. 1983-1986 STUDY This was the largest case control study on lung cancer in women in Hong Kong. A standardized structured questionnaire was designed for interviewing. All the cases were confirmed pathologically. They were compared with 445 female healthy neighbourhood controls metched for age. The RR of ever smoking was 3.81. 45.5% of the cases were never smokers. For never smoking women, 57.8% of the cases and 45.4% of the controls had passive smoking due to a smoking husband. The RR for passive smoking was 1.65 (P<0.81, 95% C.I.-1.16, 2.35). ~ ; When broken down by cell type, the proportion of never smokers of 62.41 was the highest in adenocarcinoma and it was only in this cell type that the RR for passive smoking was statistically significant (RR-1.87, P<s.01, 95% C.I.-1.23, 2.85). Significant trends for RR with amount smoked daily by husband were observed for all cell tyges combined and for adenocarcinoma only. TABLE I SU!lMARY' (F RESULTS ON PASSIVE SlqRING A14flNG Ii0li-ShyJRING WOMEN IN 4 CASE CXaNfRCi. SZVDIES IN BoNG ROI4G Cases/Controls Study* Passive smoking No passive smoking Total no. of cases i controls Relative risk P value 1976-1977 34/66 50/73 223 0.75 0.38 Chan & Fung, 1983 1981-1983 54/71 34/66 225 1.48 0.16 Koo et al, 1985 1981-1984 37/64 23/80 204 2.01 0.03 Lam A)E, 1985 1983-1986 115/152 84/183 534 1.65 0.007 Lam TH et al, 1987 Grand Total 240/353 191/402 1,186 1.43** 0.004 N 0 • The study by Lam WK included only adenocarcinoma whereas the other three studies included all cell types. ** Sumoary relative risk by Mantel Baenszel'i sethod

281 SOMMARY OF RESULTS QN PASSIVE STlORING Table I shows the summary of results of the above four studies. Apart fran the earliest study in which only one simple question was asked about passive smoking, they allishowed a RR greater than unity. Statistical significance was reached in the recent two. The Mantel* ` ~ eaenszel's summary RR was 1.43 (P<0.a1, 95% C.I.-1.12, 1:83):F '' in a review of epidemiological and other evidence on passive smoking and lung cancer, Blot and Fraumeni estimated a 30% excess risk6 while Wald et al calculated a relative risk of 1.35 by pooling the results of ten case control studies and three prospective studies.7 The summary RR of the four case control studies in Hong Kong is close to these estimat6s. Because the local prevalence of smoking among women was low (4.1!), the influence by misclassification bias would be much less than in western countries and could not account for the relatively high RR. 3l:e results in Hbng„iCong; tt:erefoc.e~~trongly suggest_ that passive smoking ~+ ~'is{a risk factor for lung cancer in never smoking Chinese women. ISCRNCiGF.DGEMENf We thank the International Development Research Centre and the pniversity of Hong Kong (Comnittee on Research and Conference Grant and Medical Faculty Research Grant Fund) for financing the research project. Thanks are also due to Dr. D.W. Ban and Dr. Keith Arnold for their support, to Roche Asian Research Foundation for sponsoring our presentation of the paper and to Mr. Richard Peto for his ccsanents. REFERENCES 1. Chan WC, Colbourne [i7, Fung SC, Ho HC (1979) Br J Cancer 39:182-192 2. Chan WC, Fung SC (1982) In: Grundmann E(ed) Cancer Campaign, Vol 6, Cancer Epidemiology, Fischer Verlag, Stuttgart and New York, pp 199- 201 3. Koo LC, Ho JHC, Lee N (1985) Int J Cancer 35:149-155 4. Lam WK (1985) A clinical, and epidemiological study of carcinoma of lung in Hong Kong. M.D. Thesis, University of Hong Kong, Hong Kong 5. Lam TH, Rung ITM, Wong CM, Lam WR, Rleevens JWL, Saw D, Hsu C, Seneviratne S, Lam SY, Lo RiC, Chan WC (1987) Br J Cancer 56:673-678 6. Blot WJ, Fraumeni JF Jr (1986) J Natl Cancer Inst 77:993-1000 7. Wald NJ, Nanchahal K, Thompson 8G, Cuckle HS (1986) Br Med J 293: 1217-1222 B. Hong Kong Census and Statistics Department (1985) Special Topics Report III, Social Data Collected by the General Household Survey. Government Printer, Hong Kong v