Outcomes in patients with pT3N0M0 breast cancer with and without postmastectomy radiotherapy

Abstract Background The role of adjuvant postmastectomy radiotherapy (PMRT) remains controversial for patients with pT3N0M0 breast cancer after mastectomy, especially when patients were treated with the updated adjuvant chemotherapy and much more advanced radiation technology. The present analysis compared locoregional recurrence-free survival (LRFS), disease-free survival (DFS), and breast cancer-specific survival (BCSS) in pT3N0M0 patients treated with mastectomy, stratified by PMRT use.Methods Between October 2000 and 8 September 2016, the database of the Breast Cancer Center of Shanghai yielded 114 patients with node-negative non-metastatic breast cancer with tumors >5 cm. Fifty-nine (51.8%) received adjuvant PMRT. Univariate and multivariate analysis were performed to assess the risk factors for survival. Differences between the two groups were compared using the log-rank test.Results The median follow-up was 62.3 months. Five-year LRFS was 100% in the PMRT group vs. 98.1% in the non-PMRT group (P=0.17); 5-year DFS was 93.2% in the PMRT group vs. 90.5% in the non-PMRT group (P=0.40). Univariate analysis identified a family history of malignant tumors, lymphovascular invasion (LVI), or triple-negative breast cancer (TNBC) molecular subtype were associated with higher locoregional recurrence (LRR) (P<0.05); furthermore, patients who were estrogen receptor-negative (P=0.0593) or who had grade 3 histologic features (P=0.0776) tended to have a higher rate of LRR. No PMRT was the only risk factor independently associated with poorer DFS (P=0.042) on multivariate analysis. No difference in BCSS was observed between the two groups.Conclusions The present study demonstrated a low LRR rate and good survival for node-negative breast cancer >5 cm. PMRT tended to improve LRFS and significantly improved DFS. Patients with risk factors including positive family history, TNBC subtype, LVI positivity, and grade 3 disease are at high risk for LRR and might benefit from PMRT.