Family history of breast cancer in relation to tumor characteristics and mortality in a population-based study of young women with invasive breast cancer.

Inherited predisposition may be associated with distinctive breast cancer phenotypes and/or mortality. Past studies have had inconsistent results and little is known about the contributions of screening and treatment.,Within a population-based cohort of 1,260 women diagnosed with invasive breast cancer before age 46, we assessed how family history of breast cancer relates to mortality and tumor characteristics. Analyses were repeated excluding BRCA1/BRCA2 carriers. Medical records were reviewed for treatment history and tumors were centrally reviewed and tested. Cox proportional hazard modeling was used to assess the risk of dying in relation to family history; logistic regression was used to assess the association of family history to tumor characteristics.,Compared with women with no family history, women with first-degree family history of breast cancer had a 40% reduction (95% CI: 0.5-0.8) in the risk of dying. Mortality in women with only a second-degree family history was similar to those with no family history. The risk of dying was further reduced in those with a greater number of affected relatives. These relationships did not seem to be attributable to differences in screening, detection method, or treatment. Tumors in women with a first-degree family history had generally more favorable prognostic profiles.,Our findings suggest that breast cancer patients with a first-degree family history, compared with their counterparts without such a profile, may have a better prognosis.,These findings support the need for future research directed at replicating these results and identifying factors underlying this possible relationship.