FAMILIAL RISKS IN IN-SITU CANCERS FROM THE FAMILY-CANCER DATABASE

The Swedish Family-Cancer Database was used to analyze relationships b etween parents and offspring with in situ cancers and between in situ cancers in one generation and invasive cancer in the other generation. A total of 130,000 in situ cancers and close to 400,000 invasive canc ers were included from 1959 to 1994, The data on family relationships and cancers came from registered sources and should be free from bias. The offsprings' familial relative risks (FRRs) were calculated for co ncordant and discordant parental cancer sites. The most common male in situ site was skin (both melanoma and precancerous epithelial lesion) , whereas cervix, breast, and skin were common female sites. Increased FRRs were observed for concordant sites: colon, breast, cervix, skin (melanoma), and, in males, precancerous epithelial lesions. The findin gs were consistent when in situ cancer-in situ cancer and in situ canc er-invasive cancer relationships were explored. FRRs were higher for i n situ colon cancer and melanoma than the respective estimates in inva sive cancers, and for the remaining sites, they were equal or somewhat lower, At discordant sites, increased FRRs of in situ cancers were ob served for female breast and melanoma and, at many sites, implicated i n tobacco and human papilloma virus carcinogenesis, together with cerv ix, Family histories of ill situ cancers deserve clinical attention.