Cancers of the breast and female genital system: search for recessive genetic factors through analysis of human isolate.

To investigate the importance of recessive genes in female breast and genital cancers, we have conducted investigations in the Hutterites, a highly inbred genetic isolate in North America. The homogeneous life style of this group, which lives on communal farms, also facilitates distinction between shared environmental and genetic factors. We ascertained 177 cases of cancer (all organ systems) through Canadian and United States cancer registries, field trips, and searches of death certificates. Breast cancer and endometrial cancer mortalities were those expected for 1970 United States whites, but no deaths due to squamous cervical carcinoma were ascertained in this monogamous population. Inbreeding coefficients (F) for cases were higher than means for matched controls for each of the four cases of breast cancers that occurred in younger women (less than 45 years of age), for four of five cases of endometrial cancer, and for the single cases of uterine leiomyosarcoma, dysgerminoma, and ovarian adenocarcinoma. By contrast, in cases of breast cancer that occurred in women 45 years of age or older, only four of 15 F's were above those for controls. There is a significant difference between the two breast cancer age groups with respect to the likelihood that the F of cases was higher than the F of controls (chi 2 = 6.99, p less than 0.01). However, grouping cases by type, none of the F distributions were significantly different from those of their matched controls. These preliminary genetic investigations thus conform certain concepts concerning breast and female genital cancer but also suggest the desirability of further studies to elucidate the role of genetic factors in premenopausal breast cancer.