Long-term Outcomes for Neoadjuvant Versus Adjuvant Chemotherapy in ER+/HER2- Locally Advanced Breast Cancer

The effectiveness of neoadjuvant chemotherapy (NaCT) over adjuvant chemotherapy (ACT) in enhancing long-term survival for ER+/HER2- breast cancer patients is uncertain. This study compares breast cancer-specific survival (BCSS) between these treatments in patients with stage IIB-IIIC ER+/HER2- breast cancer using the SEER database.

Data from 46,837 patients who underwent chemotherapy and surgery from 2010-2019 were analyzed. Breast cancer-specific survival was assessed by using multivariable Cox regression, inverse probability of treatment weighting (IPTW), and propensity score-matching (PSM) models, along with subgroup analyses.

Of the study cohort, 78.4% received ACT, and 21.6% received NaCT. Neoadjuvant chemotherapy usage increased from 15.6% in 2010 to 31.4% in 2019. Multivariable analysis indicated a lower BCSS in the NaCT group (hazard ratio [HR] 1.39, 95% confidence interval [CI] 1.31-1.48, P < 0.001), a trend consistent in IPTW and PSM analyses. However, in specific subgroups, particularly younger patients (<40 years) achieving pathologic complete response (pCR), the NaCT group exhibited better BCSS.

Overall, NaCT was associated with poorer survival compared to ACT in ER+/HER2- breast cancer. Nonetheless, certain subgroups, especially younger patients achieving pCR, showed potential benefits from NaCT. Future research should aim to identify markers for optimally applying NaCT in ER+/HER2- breast cancer treatment.