The efficacy of adjuvant chemoendocrine versus endocrine therapy alone in hormone receptor-positive, HER2-negative early breast cancer: A meta-analysis of reconstructed individual patient data.

Abstract

e12504 Background: The benefit of adding adjuvant chemotherapy to endocrine therapy for hormone receptor–positive (HR+), HER2-negative (HER2-) early breast cancer remains controversial, particularly in the era of genomic risk stratification. This meta-analysis evaluated long-term survival outcomes of chemoendocrine therapy (CET) versus endocrine therapy alone (ET) in this population. Methods: PubMed, EMBASE, and the Cochrane Library were searched for randomized controlled trials (RCTs) comparing CET with ET in HR+/HER2– early breast cancer. Individual patient time-to-event data were reconstructed from published Kaplan–Meier curves. Pooled hazard ratios (HRs) for overall survival (OS), invasive disease-free survival (IDFS), and distant disease-free survival (DDFS) were estimated using Cox frailty models. The proportional hazards assumption was tested, and restricted mean survival time (RMST) analyses quantified absolute survival differences. Results: Five RCTs including 13,866 patients met inclusion criteria. The addition of chemotherapy did not significantly improve OS (HR = 0.90; 95% CI 0.77–1.06; P = 0.221) or DDFS (HR = 0.92; 95% CI 0.74–1.15; P = 0.464). A statistically significant but clinically modest improvement was observed in IDFS (HR = 0.90; 95% CI 0.82–0.99; P = 0.035), corresponding to an RMST difference of only 0.07 years at 9 years. No violation of proportional hazards assumptions was detected. Conclusions: Among patients with HR+/HER2– early breast cancer, adjuvant chemotherapy added to endocrine therapy does not yield a significant overall survival benefit and offers only a minimal, clinically questionable improvement in invasive disease-free survival. These findings suggest that endocrine therapy alone is sufficient for most patients with low to intermediate genomic risk.