Retrospective cohort study of reproductive factors and risk of contralateral breast cancer by age and hormone receptor status

A retrospective cohort study by The California Breast Cancer Survivorship Consortium investigated the association of reproductive factors with risk of contralateral breast cancer (CBC). Among 8045 women with a first primary invasive breast cancer between 1994 and 2009, 532 CBC were identified. Associations with reproductive factors were observed only in younger FBC patients diagnosed at age < 50 years. In younger survivors of HR-negative FBC, higher risk of CBC was associated with longer duration of breast feeding. The authors conclude that younger FBC survivors who are nulliparous or had a full term pregnancy less than 10 years before FBC diagnosis may benefit from more frequent surveillance screening after FBC diagnosis.