Long-Term Survival Benefit With Adjuvant Tamoxifen in Premenopausal Women With Estrogen Receptor–Positive Breast Cancer
As reported by Ekholm et al in the Journal of Clinical Oncology, 25-year follow-up of a Swedish phase III trial suggests a survival benefit with 2 years of adjuvant tamoxifen vs no systemic treatment in premenopausal women with estrogen receptor–positive stage II primary breast cancer.
Study Details
In the trial, 564 women with breast cancer irrespective of hormone receptor status were randomized to 2 years of tamoxifen (n = 276) or no systemic treatment (n = 288) between 1984 and 1991. Data on date and cause of death were obtained from the Swedish Cause of Death Register.
Survival Outcomes
Median follow-up for 250 patients alive in April 2014 was 26.3 years. Among all patients, tamoxifen was associated with trends in improvement in cumulative mortality (hazard ratio [HR] = 0.82, P = .080) and cumulative breast cancer mortality (HR = 0.81, P = .090). Among 362 patients with estrogen receptor–positive tumors, the hazard ratios were 0.77 (P = .075) for cumulative mortality and 0.73 (P = .046) for cumulative breast cancer mortality.
Among patients with estrogen receptor–positive disease, the effect of treatment appeared to vary over time. For cumulative mortality, hazard ratios were 1.05 (95% confidence interval [CI] = 0.64–1.73) for 0 to 5 years, 0.58 (95% CI = 0.37–0.91) for 5 to 15 years, and 0.82 (95% CI = 0.48–1.42) after 15 years. For cumulative breast cancer mortality, hazard ratios were 1.09 (95% CI = 0.65–1.82) for 0 to 5 years, 0.53 (95% CI = 0.33–0.86) for 5 to 15 years, and 0.72 (95% CI = 0.36–1.44) after 15 years.
The investigators concluded: “Two years of adjuvant tamoxifen resulted in a long-term survival benefit in premenopausal patients with estrogen receptor–positive primary breast cancer…. A vast majority of patients did not receive adjuvant chemotherapy, enabling a study of the long-term effect of tamoxifen independent of the benefit of modern chemotherapy.”
The study was supported by Futurum–Academy of Health and Care, Jönköping County Council; the Medical Research Council of Southeast Sweden, the Swedish Cancer Society, and others.
Maria Ekholm, MD, of Lund University, Sweden, is the corresponding author of the Journal of Clinical Oncology article.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
