Influence of Postmastectomy Radiotherapy on Overall Survival in Patients With Clinical Prognostic Stage I-III Breast Cancer With Positive Responses and Achieving YPN0 Following Neoadjuvant Therapy: A Propensity Score Matching Based on the SEER Database.

Introduction: The role of postmastectomy radiotherapy (PMRT) in clinical prognostic stage I-III breast cancer patients with positive responses and achieving ypN0 after Neoadjuvant therapy (NAT) is controversial.

Methods: 3557 patients with TNM clinical prognostic stage (AJCC 8th Edition) I-III breast cancer with positive responses and achieving ypN0 following neoadjuvant therapy were selected from the Surveillance, Epidemiology, and End Results (SEER) database and followed through the end of 2020. COX proportional hazards models were employed to examine the associations between clinical or pathological parameters and OS. Propensity score matching (PSM) was employed to control for confounding variables and multiple association inference models were used for progressive sensitivity analysis.

Results: In the multivariate analysis, PMRT did not demonstrate a significant improvement in OS (P = .127), while in univariate analysis, it was linked to worse OS (P < .001). PSM and multiple association inference models indicated that PMRT did not confer any significant improvement in patients' OS (all P > .05). Further stratified analysis of the prematch subgroup revealed that PMRT was linked to the 68% lower risk of mortality in patients with the cN3 subgroup (HR: 0.32; 95%CI, 0.11-0.97), and expressly enhanced the OS in cN3 subgroup patients with ER-, PR-, HER-2- status, and PR to NAT.

Conclusions: Our research indicated that PMRT did not show any survival benefits for clinical prognostic stage I-III breast cancer patients who had positive responses and achieved ypN0 after NAT. PMRT was linked to the reduction in mortality among patients in the cN3 subgroup.