Independent of Known Cancer Predisposition Syndromes Complex Genotype Sarcomas Display Familial Inheritance

Background: The low incidence of sarcomas in the general population makes heritable contribution to disease risk difficult to discern beyond highly penetrant Mendelian syndromes. Methods: The Utah Cancer Registry (UCR) and Utah Population Database were interrogated for sarcoma diagnostic codes grouped by genetic type, either complex genotype/karyotype sarcoma or balanced translocation-associated sarcoma. The genealogic index of familiality (GIF) was calculated and relative risks (RR) of disease estimated for first-, second-, and third-degree relatives of sarcoma probands. Cancer patterns in pedigrees of sarcoma probands were examined to rule out known hereditary cancer syndromes. Results:A total of 229 balanced translocation type and 1,161 complex genotype type sarcomas with at least three generations of ancestral genealogy data were identified in the UCR. There was no evidence for excess relatedness for the balanced translocation group by using the GIF test (P1⁄4 0.657) and no significantly elevated RRs. In the complex genotype group, we observed significantly elevated GIF (P 1⁄4 0.03). Modest RRs corroborated the GIF analysis, in which excess relatedness existed in distant relationships. No recognized cancer syndromes were identified among high-risk pedigrees. Discussion:We identified strong familiality among complex genotype sarcomas, independent from known cancer predisposition syndromes. In the absence of significantly elevated RRs for close relatives, the high GIF argues for a strong genetic—rather than environmental—component to complex genotype sarcoma risk. We observed no significant familial risk of developing balanced translocation-associated sarcomas, but the