Background: The role of postmastectomy radiotherapy (PMRT) in breast cancer patients achieving pathologically negative lymph nodes (ypN0) after neoadjuvant chemotherapy (NAC) remains controversial due to heterogeneous recurrence risks and lack of prospective evidence. Objectives: To evaluate the effects of PMRT in ypN0 patients after NAC. Design: Multicenter retrospective study. Methods: Data of 624 breast cancer patients with ypN0 was assessed to establish a recurrence risk score model based on a disease-free survival (DFS) rate-based multivariate Cox model. Moreover, the locoregional control (LRC), DFS, and overall survival (OS) rates in PMRT and non-PMRT patients were calculated using the Kaplan–Meier method. Results: All patients received a median of four NAC cycles, followed by mastectomy and axillary lymph node dissection; moreover, 257 (41.2%) patients underwent PMRT. Over a median follow-up duration of 74 months, the 5-year LRC, DFS, and OS rates for all patients were 96.6%, 90.1%, and 95.7%, respectively. The differences in the LRC, DFS, and OS rates between PMRT and non-PMRT patients were nonsignificant in the univariate and multivariate analyses. By using our recurrence risk score model based on four factors (i.e., age, clinical N stage, NAC cycle number, and pathological tumor stage after NAC), we stratified the patients into low- and high-risk groups; their 5-year rates of LRC (98.8% vs 93.9%), DFS (95.1% vs 83.8%), and OS (98.4% vs 92.4%) were significantly different (all p < 0.05). PMRT improved LRC (97.6% vs 90.8%, p = 0.027) but not DFS or OS in high-risk patients and had no benefit in low-risk patients. Conclusion: Our recurrence risk score model effectively distinguished ypN0 patients with different recurrence risk stratifications. PMRT improved LRC but not DFS or OS in high-risk patients and low-risk patients did not benefit from PMRT.
Wang et al. (Mon,) studied this question.
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