ARTICLES Contralateral Primary Tumors in Breast Cancer Patients in a Randomized Trial of Adjuvant Tamoxifen Therapy

Prophylactic treatment with the anti-estrogen tamoxifen may reduce the risk of breast cancer because estrogens are thought to act as promoters in the pathogenesis of the dis-ease. This article presents results on the incidence of con-tralateral new primary tumors among 1846 postmenopausal breast cancer patients included in a randomized trial of ad-juvant tamoxifen therapy for 2 or 5 years after surgery ver-sus no adjuvant endocrine therapy. The median follow-up was 7 years (range, 3-13 years). There was a significant reduction of contralateral breast cancer in the 931 patients in the tamoxifen group versus that in the 915 control patients (29 versus 47 cases, respectively; P =.03). The cumulative incidence at 10 years in the tamoxifen group and the control group was 5 % and 8%, respectively. Analysis of the relative hazard of contralateral tumor over time showe