Does a family history of cancer increase the risk for postmenopausal endometrial carcinoma? A prospective cohort study and a nested case-control family study of older women

BACKGROUND. As part of the hereditary nonpolyposis colon carcinoma (HNPCC) constellation of neoplasia caused by defects in mismatch repair genes, some endometrial carcinomas are known to have a genetic contribution to etiology. However, most endometrial carcinomas occur in postmenopausal women, presumably without the HNPCC defect. Consequently, the genetic contribution to these cases is unclear. The objective of this study was to determine whether family history of cancer is a risk factor for endometrial carcinoma in older women. METHODS. The authors analyzed incident endometrial carcinoma data, as welt as data on family history of various cancers in first-degree relatives, from a cohort of 24,848 postmenopausal Iowa women ages 55-69 years who were cancer free at baseline in 1986. Because a positive family history is dependent on many factors, including the age of the patient, the number of relatives, and the distribution of other risk factors in relatives, the authors also conducted a nested case-control study on family members of 95 patients with endometrial carcinoma diagnosed during 1988-1989 and 91 cancer free controls who were chosen randomly from subjects matched for age (±1 year). RESULTS. During 10 years of follow-up of the cohort, 322 incident endometrial carcinoma cases occurred. Women who reported a positive family history of cancer overall or at any specific site (e.g., the endometrium, colon, or breast) were not at increased risk for endometrial carcinoma. Adjustment for potential confounders, such as age, obesity, parity, oral contraceptive use, and estrogen replacement therapy, did not alter these results. Analysis of the family members of the cases and controls produced little evidence to suggest that this lack of association between family history and endometrial carcinoma could be explained by unequal distribution of known risk factors among relatives. Case family members were slightly older than control family members, but no significant differences were found in body mass index (kg/m²), age at menarche, age at menopause, or number of pregnancies. Relation to a case or control was not associated with increased risk of endometrial, ovarian, breast, or colon carcinoma for family members. Controlling for a variety of potential confounders did not alter the results. CONCLUSIONS. No evidence was found that genetics contribute to the risk of postmenopausal endometrial carcinoma for women with no personal cancer history.