The effect of postmastectomy radiotherapy in node-positive triple-negative breast cancer

Background The value of postmastectomy radiotherapy (PMRT) for pathological node-positive triple-negative breast cancers (TNBC) remains debatable. The aim of this population-based retrospective study was to evaluate the effect of PMRT on survival outcomes in this population. Methods Patients diagnosed with stage T1-4N1-N3M0 TNBC between 2010 and 2014 were identified from the Surveillance, Epidemiology, and End Results (SEER) database. We used univariate and multivariate Cox regression hazards method to determine the independent prognostic factors associated with 3-year breast cancer-specific survival (BCSS). The effect of PMRT on 3-year BCSS was analyzed after stratification by pathological staging of groups. Results Of the 4398 patients included in this study, 2649 (60.2%) received PMRT. Younger age, black ethnicity, and advanced tumor (T) and nodal (N) stage were the independent predictors associated with PMRT receipt (all P < 0.05). Patients who received PMRT showed better 3-year BCSS (OR = 0.720, 95% CI = 0.642–0.808, P < 0.001) than those that did not. The effect of PMRT on 3-year BCSS was analyzed after stratification by pathological staging of groups. The results showed that PMRT was associated with better 3-year BCSS in patients with stage T3–4N1 ( P = 0.042), T1-4N2 ( P < 0.001), and T1-4N3 ( P < 0.001), while comparable 3-year BCSS was found between the PMRT and non-PMRT cohorts with T1–2N1 disease ( P = 0.191). Conclusions Radiotherapy achieved better 3-year BCSS in TNBC patients with stage T3–4N1 and T1-4N2–3 disease. However, no survival benefit was found with the addition of PMRT in patients with T1–2N1 TNBC.