Familial Aggregation of Lung Cancer in Humans2

Analyses of data from a comparison of relatives of 270 lung cancer probands with those of the race-sex-age-residence matched controls indicate a significant excess in the lung cancer mortality among proband relatives. This excess mortality was not accounted for by age, sex, generation, and cigarette-smoking factors. No such relationship was found among spouses of the two groups. The data further revealed: 1) The familial effect is more marked among nonsmokers than among smokers. 2) The smoking effect is more evident among control relatives than among proband relatives. 3) The effect of cigarette smoking may be greater, at least in men, than that of the familial factor; however, in women the effect of familial factor may be greater than that of the smoking factor. 4) The effect of the familial factor among nonsmokers is similar in both men and women. 5) There is a synergistic interaction between the familial and smoking factors. 6) Blood relatives of the probands are more likely to be smokers than those of the controls. 7) There is among the case relatives a substantial excess mortality attributed to noncancer respiratory diseases, which suggests that the case relatives have certain common susceptibility to all respiratory diseases. 8) No significant differences were observed between the spouses of the case and control subjects with respect to smoking habits and noncancer respiratory diseases, respectively. From the totality of all results it would appear that genetic factors may play a role in the etiology of lung cancer, together with such environmental factors as cigarette smoking.