Familial clustering of endometrial cancer in a well-defined population.

OBJECTIVE: Using a genealogical database, we examined risk of endometrial cancer among family members of individuals with endometrial cancer. METHODS: We identified endometrial cancer cases in the Utah Population Database (UPDB), a computerized archive of genealogy data linked to the Utah Cancer Registry. We tested for excess relatedness and estimated relative risks (RR) among first-, second-, and third-degree relatives of endometrial cancer cases and stratified analyses by tumor histology and body mass index (BMI). RESULTS: We identified 3911 cases; 3546 were Type I cancers and 365 Type II cancers. The RR for all endometrial cancer cases and for cases with type I histology was significantly increased for first-, second-, and third-degree relatives. An almost three-fold risk was observed among first-degree relatives of individuals with Type I cancers and a 2.24-fold risk among second-degree relatives of Type I morbidly obese cases. The magnitude of endometrial cancer risk among relatives appeared to increase with case BMI. CONCLUSIONS: The elevated risks for endometrial cancer among first-, second-, and third-degree relatives support a genetic contribution to predisposition to endometrial cancer. The increased risk appears to be limited to Type I endometrial cancer. We observed increased risks for endometrial cancer among relatives of obese and morbidly obese Type I cases, which may be indicative of a synergistic relationship between underlying genetic propensity and shared environment. This study quantifies risk of developing cancer among relatives of patients with disease and provides the basis for further analysis of high risk pedigrees and gene identification for genetic etiologies of endometrial cancer.