Two years of tamoxifen or no adjuvant systemic therapy for patients with high-risk breast cancer: long-term follow-up of the Copenhagen breast cancer trial

Abstract

Background: The Copenhagen Breast Cancer Trial (CBCT) randomly assigned patients with early breast cancer to two years of tamoxifen or placebo and we evaluated the effect over the following four decades.Patient and methods: Between 1975 and 1978, 327 patients with primary breast cancer were randomly assigned to two years of daily placebo or tamoxifen. Survival statistics was collected from the Danish Civil Registration System.Results: The five-year invasive breast cancer recurrence (BCR) rate was 43.2% in the placebo arm and 31.9% in the tamoxifen arm. Compared with the placebo arm the hazard ratio for a BCR event was 0.73 in the tamoxifen arm (p = .07). With an estimated median follow-up on overall survival of 40.9 years, 154 and 145 patients had died in the placebo and tamoxifen arm, respectively. After adjustment for baseline characteristics a significant reduction in mortality was obtained from tamoxifen (HR 0.79; p = .04).Conclusion: Two years of adjuvant tamoxifen resulted in a sustained reduction in mortality in pre- and postmenopausal high-risk breast cancer patients with long-term follow-up data.