Abstract

Purpose
This study aimed to evaluate the impact of postoperative adjuvant chemotherapy (AC) on survival outcomes in breast cancer (BC) patients who have already undergone neoadjuvant chemotherapy (NAC) followed by surgery.
Materials and Methods
Data from a population-based cohort (2010-2020) were analyzed for BC patients treated with NAC and surgery. Univariate and multivariate Cox regression identified prognostic factors for overall survival (OS), and a nomogram was developed and validated. Personalized scores from the nomogram were used for risk stratification to assess the effect of postoperative AC.
Results
A total of 15,921 BC patients were analyzed, with 11,144 in the training cohort and 4,777 in the validation cohort. The key prognostic indicators for OS included age, race, marital status, histological grade, breast cancer subtype, T stage, N stage, type of surgery, and response to NAC (all p<0.05). The nomogram effectively predicted individualized OS rates and stratified patients into various risk categories. Postoperative AC was found to significantly enhance OS in the high-risk subgroup (p=0.011 in the training cohort, p=0.012 in the overall population). However, for the low-risk subgroup, there was no significant survival benefit from postoperative AC (p=0.130 for the training cohort, p=0.588 for the overall population), suggesting that some patients might safely forgo unnecessary postoperative AC.
Conclusion
This study efficiently differentiates between varying levels of risk, enabling clinicians to identify patients unlikely to benefit from postoperative AC and thus reduce the likelihood of overtreatment.

• Keywords: Breast neoplasms, Neoadjuvant therapy, Adjuvant chemotherapy, Prognosis, Nomograms, Risk stratification