Increased familial risk for non-lung cancer among relatives of lung cancer patients.

Reports of two or more anatomically distinct cancer types clustering in families suggest the possible existence of a susceptibility-to-cancer gene. To determine whether a genetic predisposition accounts for such familial aggregation, a retrospective case-control study was conducted in 1976-1979 of 337 southern Louisiana families in each of which a deceased lung cancer patient was used as the proband. A comparison of first-degree relatives of proband families with spouse (control) families revealed a significantly greater overall risk of cancer (odds ratio (OR) = 2.0, p less than 0.0001) in the proband group. Using logistic regression techniques to control for the confounding effects of age, sex, cigarette smoking, and occupational/industrial exposures, relatives of lung cancer probands maintained an increased risk of non-lung cancer (p less than 0.05). The crude odds ratio of a proband family having one family member with cancer was 1.67 compared with control families. Proband families were 2.16 times more likely to have two other family members with cancer. For three cancers and four or more cancers, the risk increased to 3.66 and 5.04, respectively. Each risk estimate was significant at the 0.01 level. The most striking differences in cancer prevalence between proband and control families were noted for cancer of the nasal cavity/sinus, mid-ear, and larynx (OR = 4.6); trachea, bronchus and lung (OR = 3.0); skin (OR = 2.8); and uterus, placenta, ovary, and other female organs (OR = 2.1). These data support the hypothesis of a genetic susceptibility to cancer in families with lung cancer.