BACKGROUND.
This study investigates whether a positive family history of breast carcinoma is associated with improved survival after invasive breast carcinoma among women ages 21 through 45. METHODS. Subjects were 733 nonadopted women born after 1944 who were diagnosed with primary invasive breast carcinoma between January 1983 and April 1990 while residing in the metropolitan Seattle area and who provided information on family history of breast carcinoma. Information on clinical characteristics and survival was obtained from a population-based cancer registry. Subjects were followed for survival through 1994. Cox proportional hazards models were used to estimate the relative risk (RR) of dying in relation to family history of breast carcinoma, adjusting for selected clinical characteristics, age and year of diagnosis, and prior mammograms. RESULTS. The risk of dying among women with a first-degree family history of breast carcinoma was half that of women with no family history of breast carcinoma (RR = 0.5; 95% confidence interval [CI], 0.3-0.9). There was no evidence of a reduction in the risk of dying among women with only a second-degree family history of breast carcinoma (RR = 1; 95% CI, 0.6-1.4). These associations were adjusted for age and year of diagnosis, stage of disease, tumor size, bilaterality, and mammogram history. These findings were not further influenced by adjustment for initial treatment or the numbers and ages of relatives at risk for breast carcinoma. CONCLUSIONS. Compared with women with neither a first-nor second-degree family history of breast carcinoma, the authors found that women who had a firstdegree family history experienced increased survival. This finding did not appear to be attributable to differences in screening or treatment. To the extent that this difference is attributable to underlying biologic mechanisms, new insights into the natural history and treatment of breast carcinoma could result. Future studies should investigate whether specific susceptibility genes are associated with differential survival from breast carcinoma.