Cancer in the offspring of parents with lung cancer

Despite several studies on the role of passive smoking in the development of childhood cancer, particularly leukaemia, lymphomas and brain cancer, no definitive answer has yet been provided. The aim of the cohort study reported here was to analyse the incidence of cancer in the offspring of young lung cancer patients on the basis of the assumption that all of the offspring were exposed passively to smoke. The files of the Danish Cancer Registry provided 3348 cases of lung cancer patients born after 1935, and their offspring (n = 6417) were identified through the Danish Population Register. The files of the offspring were then linked with the files of the Danish Cancer Registry and the numbers of cancers observed in the offspring were compared with those expected from national age-specific and calendar-time-specific rates. A total of 135,333 person-years was the basis for analysis. Twenty-six cancers were observed, with 30.3 expected, yielding a standardised incidence ratio (SIR) of 0.9 (90% confidence interval (CI), 0.6-1.2). There was no excess of brain tumours, leukaemias or lymphomas. Stratification for sex of the lung cancer patients revealed a non-significantly increased risk for both non-Hodgkin's lymphoma (three cases; SIR = 3.4; 90% CI: 0.9-8.7) and Hodgkin's disease (three cases; SIR = 2.6; 90% CI: 0.7-6.6) in the offspring of female lung cancer patients. These results suggest that there is little evidence of an excess cancer risk in childhood, whether due to passive smoking or to as yet unidentified genetic factors, among the offspring of people who develop lung cancer. However, the results are limited by the fact that exposure was only assessed indirectly, with no measurement of actual cigarette consumption made.