Long-Term Follow-up of Intergroup Exemestane Study
A final efficacy analysis of the Intergroup Exemestane Study, reported in the Journal of Clinical Oncology by Morden et al, shows continued benefit of switching to adjuvant exemestane after 2 to 3 years of tamoxifen in patients with early breast cancer.
Study Details
In the trial, patients who remained disease free after 2 to 3 years of adjuvant tamoxifen were randomized to continue tamoxifen or switch to exemestane, for a total of 5 years of adjuvant endocrine therapy. Breast cancer–free survival, with censoring of intercurrent deaths, among 4,599 patients with estrogen receptor–positive disease or tumors without known estrogen receptor status was the primary survival endpoint of interest for the current analysis.
Survival Outcomes
At the time of analysis, median follow-up was 120 months. Breast cancer–free survival events had occurred in 508 of 2,294 patients (22.1%) in the exemestane group and 603 of 2,305 patients (26.2%) in the tamoxifen group, with an absolute difference at 10 years of 4.0% and a hazard ratio (HR) of 0.81 (95% confidence interval = 0.72–0.92). The difference remained significant in multivariate analysis adjusting for nodal status, prior use of hormone replacement therapy, and prior chemotherapy (HR = 0.80, P < .001). A nonsignificant improvement in overall survival was observed for exemestane (absolute difference = 2.1%; HR = 0.89, P = .08). There was no significant difference in incidence of fracture in the posttreatment period (9.3% vs 8.0%, P = .14).
The investigators concluded: “The Intergroup Exemestane Study and contemporaneous studies have established that a strategy of switching to an aromatase inhibitor after 2 to 3 years of tamoxifen can lead to sustained benefits in terms of reduction of disease recurrence and breast cancer mortality.”
The study was supported by Pfizer and Cancer Research UK.
R. Charles Coombes, MD, PhD, of Imperial College London, 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®.
