LUNG CANCER

ELSEVIER Lung Cancer I5 (1996) 381.-399

ABSTRACTS

Misclassitication of smoking habits as a source of bias in the study of environmental tobacco smoke and lung cancer Lee PN. Forey BA. l?N. Lee Statistics Computing Ltd., 17 Cedar Road, Sutton SM2 5DA. Stat Med 1996;15:581-605.

The relationship of environmental tobacco smoke to lung cancer risk in lifelong non-smokers is commonly studied using marriage to a smoker as the index of exposure. As smokers tend to marry smokers, relative risk estimates will be biased if some current or former smokers are misclassified as lifelong non-smokers. This paper shows how various factors affect the magnitude of the bias and describes a method for obtaining misclassification-adjusted relative risk estimates. Application of the method to U.S. and Asian data for women suggests misclassification is an important determinant of the slight excess risk observed in non-smokers married to smokers. Reasons why our conclusions differ from those of others are discussed, as are other difficulties in interpreting the association between spousal smoking and lung cancer risk.

Nutrition and lung cancer Ziegler RG, Mayne ST, Swanson CA. Nutrition Epidemiology Section. National Cancer Institute, Executive Plaza North 443, Bethesda, MD 20892. Cancer Causes Control 1996;7: 157-77-

Epidemiologic evidence on the relationship between nutrition and lung cancer is reviewed. Observational studies of diet and lung cancer, both prospective and retrospective, continue to suggest strongly that increased vegetable and fruit intake is associated with reduced risk in men and women; in various countries; in smokers, ex-smokers, and never-smokers; and for all histologic types of lung cancer. Prospective studies of blood B-carotene levels. arguably the best available biomarker of vegetable and fruit intake, indicate that low levels are predictive of increased lung cancer incidence. However, in a randomized, placebo- controlled clinical trial in male smokers, lung cancer incidence and total mortality were increased significantly among the men receiving R-carotene supplements. If&carotene can prevent lung carcinogenesis. which the trial cannot rule out, then the dosage, duration of use, method of administration, and/or subpopulation are critical. Ongoing clinical trials, some of which include women, will provide much needed information. Other carotenoids, other phytochemicals, and associated dietary patterns may explain the beneficial effects of vegetables and fruits and have not been explored adequately in epidemiologic work. Several observational epidemiologic studies, both prospective and retrospective. have indicated that diets high in fat. saturated fat, and cholesterol may increase the risk of lung cancer and that the effect is not mediated through vegetable and fruit intake. The relationship, although not yet established, merits further investigation. Since B- carotene can function as an antioxidant, other micronutrients with this potential, specifically vitamins E and C and selenium. also have been proposed to reduce lung cancer risk. However, the totality of the epidemiologic evidence is not, at present, persuasive for any one of these micronutrients.

Epidemiology and etiology

Compensating lung cancer patients occupationally exposed to coal tar pitch volatiles Armstrong 8, Theriault G. Environmental Epidemiology Unit, London School Hygreneflropical Med., Keppel Street. London WCIE 7HT.Dccup Environ Med 1996;53: 160-7.

Objectives - To investigate the process of deciding on compen- sation claims by lung caner patients exposed cccupationally to coal tar pitch volatiles. Methods - For each case of lung cancer the probability that it was caused (probability of causation (PC)) by coal tar pitch volatiles was expressed as an increasing limction of cumulative exposure to benzo-a-pyxene-years. This was assessed from several exposure- response models fitted to data from a large epidemiological study of ahmtinium production workers. For some models, PC depended also on the smoking habit of the cancer patient. Results - Estimation of relative risk by exposure group indicated that over 50% of lung cancers were attributable to coal tar pitch volatiless (PC >50%) at exposures above 100 &/ml-years benzo(a)pyrene. A linear relative risk model indicated that 50% PC was first achieved at 342.2 ig/m’-years benzo(a)pyrene. or 190.1 ig/m’-years benzo(a)pyrene according to the upper 95% confidence limit for risk increment. Corresponding figures for a power cmve model were 2 10.3 and 45.9. With these five figures as compensation criteria compensation would have resulted in 31.40/o, 2.7%. 19.2%. 15.7%,and39.2%ofcancersstudied,comparedwithan estimated total proportion of cancers studied attributable to coal tar pitch volatiles of 15%26%. If risks due to coal tar pitch volatiles and smoking multiply, PC does not depend on the amount smoked. If the two risks are additive, however, PC depends on the amount smoked according to a formula, with the figures mentioned applying to an average smoking history (24.4 pack-years). Conclusion -Because of its simplicity and because it falls within the range of criteria based on several more sophisticated approaches, we prefer the criterion of 100 ig/m’-years, based on the relative risks by exposure group. However, the compensation board of the Canadian province of Quebec, on consideration of these alternatives, has proposed as a criterion that the upper 95% confidence limit of PC for the patient be at least 50%. assuming an additive relative risk model and allowing for their smoking habit.

Exposure to crocidolite and the incidence of different histo- logical types of lung cancer De Klerk NH, Musk AW, Eccles JL. Hansen J, Hobbs MST. Department of Public Health, Universily of Western Australia, Perth, WA 6907. Occup Environ Med 1996;53: 157-9.

Objectives - To estimate the relations between exposure to both tobacco smoke and crocidolite and the incidence of various histological hipes of lung cancer. Methods - In 1979 all former from the Wittenocm asbestos who could be traced were Sent a questionnaire on smoking