Value of postmastectomy radiotherapy in locally advanced breast cancer patients treated with neoadjuvant chemotherapy and modified radical mastectomy

Objective To evaluate the value of postmastectomy radiotherapy (PMRT) in locally advanced breast cancer patients treated with neoadjuvant chemotherapy (neoCT) and modified radical mastectomy, and to investigate the possibility of individualized radiotherapy according to the response to neoCT. Methods We analyzed 523 patients with stage ⅢA and ⅢB breast cancer who received neoCT and modified radical mastectomy in our hospital from 1999 to 2013. Of all patients, 404 received PMRT, and 119 did not. The locoregional recurrence (LRR), disease-free survival (DFS), and overall survival (OS) rates were calculated using the Kaplan-Meier method, survival difference analysis and univariate prognostic analysis were performed using the log-rank test, and multivariate prognostic analysis was performed using the Cox regression model. Results Compared with those not treated with PMRT, the patients treated with PMRT had a significantly lower 5-year LRR rate (13.9% vs. 24.8%, P=0.013), a significantly higher DFS rate (64.1% vs. 53.9%, P=0.048), and an insignificantly higher OS rate (83.2% vs. 78.2%, P=0.389). In the patients with ypT3-T4, ypN2-N3, or pathologic stage Ⅲ disease, those treated with PMRT had a significantly reduced 5-year LRR rate (P<0.05) and a significantly increased 5-year OS rate (P<0.05), as compared with those not treated with PMRT. Among the 158 patients with ypN0 disease, the 5-year LRR rate was significantly lower in those treated with PMRT than in those not treated with PMRT (P=0.004). Of 41 patients who achieved a pathologic complete response, 2 patients, who did not receive PMRT, developed LRR. The multivariate prognostic analysis indicated that PMRT was an independent prognostic factor associated with reduced LRR in all patients and ypN0 patients. Conclusions In patients with stage ⅢA and ⅢB breast cancer treated with neoCT and modified radical mastectomy, PMRT can significantly reduce LRR for all patients and can reduce both recurrence and mortality for those with ypT3-T4, ypN2-N3, or pathologic stage Ⅲ disease. There is no sufficient evidence that PMRT can be omitted safely for ypN0 or pCR patients according to their response to neoCT. Key words: Breast neoplasms/chemotherapy; chemotherapy, neoadjuvant; Breast neoplasms/surgery; Surgery, mastectomy; Breast neoplasms/radiotherapy; Prognosis