Family history of breast cancer and its association with disease severity and mortality.

A family history (FH) of breast cancer (BC) is known to increase an individual's risk of disease onset. However, its role in disease severity and mortality is less clear. We aimed to ascertain associations between FH of BC, severity and BC-specific mortality in a hospital-based cohort of 5354 women with prospective information on FH. We included women diagnosed at Guy's and St Thomas' NHS Foundation Trust between 1975 and 2012 (n = 5354). BC severity was defined and categorized as good, moderate, and poor prognosis. Data on BC-specific mortality was obtained from the National Cancer Registry and medical records. Associations between FH and disease severity or BC-specific mortality were evaluated using proportional odds models and Cox proportional hazard regression models, respectively. Available data allowed adjustment for potential confounders (e.g., treatment, socioeconomic status, and ethnicity). FH of any degree was not associated with disease severity at time of diagnosis (adjusted proportional OR: 1.00 [95% CI: 0.85 to 1.17]), which remained true also after stratification by period of diagnosis. FH of BC was not associated with BC-mortality HR: 0.99 (95% CI: 0.93 to 1.05). We did not find evidence to support an association between FH of BC and severity and BC-specific mortality. Our results indicate that clinical management should not differ between women with and without FH, when the underlying mutation is unknown.