Risk for second primary non-breast cancer in pre- and postmenopausal women with breast cancer not treated with chemotherapy, radiotherapy or endocrine therapy

Abstract

IntroductionWe investigated the risk for a second primary cancer in pre- and postmenopausal women with breast cancer treated by surgery alone, to assess the importance of non-treatment factors and menopausal status. Patients and methodsThe cohort comprised 14,151 women with breast cancer diagnosed during 1977–2006, who did not receive radiotherapy or systemic adjuvant therapy. They were identified in the nationwide clinical database of the Danish Breast Cancer Cooperative Group. The women were followed for a second primary cancer other than breast cancer in the Danish Cancer Registry, and risk was quantified as standardised incidence ratios (SIRs). ResultsWomen with breast cancer diagnosed before menopause had an 18% greater overall risk for a second primary non-breast cancer than the general female population (95% confidence interval [CI], 1.06–1.32). The excess was confined to cancers of the endometrium (1.5; 95% CI, 1.0–2.0) and ovaries (1.8; 95% CI, 1.2–2.4). Rare histological subtypes of breast cancer were associated with these two cancer sites. Women with breast cancer after menopause had no overall excess risk for a second cancer (SIR, 0.98; 95% CI, 0.92–1.04). ConclusionAn excess risk for second non-breast cancers related to non-treatment factors is seen primarily in breast cancer patients who were premenopausal at diagnosis.