The Relation of Reproductive Factors to Mortality from Breast Cancer1

Young women with breast cancer have been reported to have an increased risk of dying from their disease if they have given birth in <2 years before diagnosis. The prognostic factors associated with the tumors of these women have not been thoroughly studied. We examined the tumors of the women who had a recent birth and compared the tumor characteristics with those of women who were nulliparous or had given birth>5 years before diagnosis. A follow-up study was conducted of 1174 women <45 years old whose invasive ductal breast cancer was diagnosed from January 1983 to December 1992 in three counties of western Washington. These women had participated previously in a population-based, case-control study. Mean follow-up time was 105.