Randomized Trial of 2 Versus 5 Years of Adjuvant Tamoxifen for Women Aged 50 Years or Older With Early Breast Cancer: Italian Interdisciplinary Group for Cancer Evaluation Study of Adjuvant Treatment in Breast Cancer 01

Purpose: To compare 2 with 5 years of adjuvant tamoxifen therapy in the treatment of early breast cancer. Patients and Methods: Women with breast carcinoma T1–3, N0–3, M0, who were between 50 and 70 years of age, were eligible irrespective of menopausal status, tumor grade, or estrogen receptor (ER) status. Patients who were event-free after 2 years of tamoxifen therapy were randomly assigned to stop or continue tamoxifen therapy for an additional 3 years. The primary end point was length of disease-free survival (DFS). Secondary end points included overall survival (OS) and toxicity. Results: From 1989 through 1996, 1,901 patients were randomly assigned either to stop treatment (n = 958) or to receive tamoxifen for 3 additional years (n = 943). The median duration of postrandomization follow-up was 52 months. We found no statistically significant differences between the 5-year arm and the 2-year arm in terms of DFS (hazard ratio [HR], 0.91; 95% confidence interval [CI], 0.76 to 1.08) and OS (HR, 1.16; 95% CI, 0.92 to 1.46). In ER-positive patients, a statistically significant prolongation of DFS related to longer treatment duration was observed (HR, 0.74; 95% CI, 0.59 to 0.93), whereas no difference in OS could be detected (HR, 0.98; 95% CI, 0.72 to 1.32). No differences in terms of endometrial cancers, cardiac or cerebrovascular events, or fractures were detected, whereas a doubling in the risk of thromboembolic events was found in the 5-year arm. Conclusion: Our results confirm previous research that shows that 5 years of tamoxifen decreases recurrence compared to 2 years in patients with ER-positive tumors.