The role of postmastectomy radiation in patients with ypN0 breast cancer after neoadjuvant chemotherapy: a meta-analysis

BACKGROUND It has been demonstrated that postmastectomy radiation therapy (PMRT) was beneficial for breast cancer patients who are axillary lymph node-positive. However, the effectiveness of radiotherapy in pathological negative nodes (ypN0) after neoadjuvant chemotherapy (NAC) remains open to considerable debate. Here, we aim to evaluate whether PMRT improves loco-regional control and survival for such patients. METHODS The literature from January 2004 to June 2019 was searched. The effects of PMRT on local-regional recurrence (LRR) and survival was evaluated in a meta-analysis. Pooled relative risk (RR) values with 95% confidence intervals (CIs) were computed using random and fixed-effect model. Subgroup and heterogeneity analyses were also conducted. RESULTS Twelve studies that included 17,747 patients met the inclusion criteria. Pooled results showed that PMRT was associated with reduced LRR (RR, 0.38; 95% CI, 0.19-0.77, P = 0.007), particularly in patients with stage III breast cancer (RR, 0.16; 95% CI, 0.07-0.37, P < 0.001). However, no significant difference in disease-free survival were observed with the addition of PMRT for ypN0 patients (RR, 0.70; 95% CI, 0.21-2.27, P = 0.55). Also, there was no statistically significant association between radiotherapy with overall survival (RR, 0.81; 95% CI, 0.64-1.04, P = 0.10). CONCLUSIONS Our meta-analysis indicated that PMRT might reduce local-regional recurrence for ypN0 patients after NAC, but lack of benefit for survival outcomes. Prospective randomized clinical trial data will be needed to confirm our results.