Estimation of genetic and environmental components in colorectal and lung cancer and melanoma

Cancer has predominant environmental and somatic causes but the assessment of hereditary (genetic) causes is difficult, except for highly penetrant si ngle-gene causes. Family studies are only partially informative in this reg ard because family members share diet and life-styles. Twin studies have be en classically used to disentangle the effects of heredity and environment on disease etiology. We estimate the genetic and environmental components i n colorectal and lung cancer and melanoma by comparing cancer risks in fami ly members. The Swedish Family-Cancer Database, comprising more than 6 mill ion individuals, was used as the source of family and cancer data. Tetracho ric correlations were used to describe similarity in cancer liability among family members. Structural equation modelling was used to derive estimates of the importance of genetic and environmental effects. The estimated gene tic component ranged from 10% in colon and colorectal cancer to 18% in mela noma. For lung cancer, the share was 14%. If assortative mating were import ant for liability to cancer, these heritability estimates may be an underes timation of the true genetic effects. Non-shared environmental effect was 6 7-68% in colorectal cancer and melanoma, and 71% in lung cancer. Shared and childhood environments were equally important in colorectal cancer and mel anoma, whereas no childhood effect was observed for lung cancer. Genet. Epi demiol. 20:107-116, 2001. (C) 2001 Wiley-Liss, Inc.