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Small cell carcinoma of the lung (SCLC) occurs most frequently in heavy smokers, yet exhibits a lesser predominance among men than other smoking-associated lung cancers. Incidence rates have increased more rapidly in women than men and at a faster rate among women than other cell types. To investigate the importance of smoking and other risk factors, a case-control study of SCLC in women was conducted. A total of 98 women with primary SCLC and 204 healthy controls, identified by random-digit dialing and frequency matched for age, completed telephone interviews. Data collected include demographics, medical history, family cancer history, residence history, and lifetime smoking habits. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated using logistic regression analysis. Risk for small cell carcinoma in women is strongly associated with current use of cigarettes. Ninety-seven of 98 cases had smoked cigarettes; 79% of cases were current smokers and 20% were former smokers at the time of diagnosis compared to 13% current and 34% former smokers among controls. The ORs associated with smoking are 108.7 (95% CI 14.8-801) for ever-use of cigarettes, 278.9 (95% CI 37.0-2102) for current smoking, and 31.5 (95% CI 4. 1-241) for former smoking. Risk increases steeply with pack-years of smoking and decreases with duration of smoking cessation. After adjusting for age, education, and lifetime smoking history, medical history of physician-diagnosed respiratory disease including chronic bronchitis, emphysema, pneumonia, tuberculosis, asthma, and hay fever is not associated with a significant increase in lung cancer risk. Employment in blue collar, service, or other high risk occupations is associated with a two to three-fold non-significant increase in risk for small cell carcinoma after adjusting for smoking.

Using data from a population-based registry, the Cancer Surveillance Program of Orange County, we examined patterns in lung cancer incidence by histological type for 1984 in Orange County, CA. Age-adjusted incidence rates per 100,000 population are 66.4 for men and 34.1 for women. Compared to 1983 rates for whites from all SEER areas combined, Orange County incidence rates are lower for men but equal for women. Squamous cell carcinoma incidence shows a strong male predominance [male/female 3.4; 95% confidence interval = (2.6, 4.4)], whereas the male/female incidence ratios for adenocarcinoma [male/female 1.4; 95% confidence interval = (1.1, 1.8)] and small cell carcinoma [male/female = 1.8; 95% confidence interval = 1.3, 2.4)] are closer to unity. Smoking habits were abstracted from medical records for 79% of cases. Only 8% of lung cancer cases (5% of men and 12% of women) with known smoking habits are nonsmokers. Adenocarcinoma is the most common cell type among women smokers and nonsmokers, while squamous cell carcinoma predominates in both male smokers and nonsmokers. Cases who smoked were younger at diagnosis than nonsmokers (P less than 0.001) for each cell type. Despite a greater proportion of nonsmokers, cases with adenocarcinoma were younger at diagnosis compared to small cell carcinoma (P less than 0.01) and squamous cell carcinoma (P less than 0.05). The observed patterns of incidence rates by histological type are not entirely explained by current knowledge of the relationship between smoking and cell type.