Does Failure to Achieve Pathologic Complete Response with Neoadjuvant Chemotherapy Identify Node-Negative Patients Who Would Benefit from Postmastectomy Radiation or Regional Nodal Irradiation?

Abstract

Postmastectomy radiation (PMRT) and regional nodal irradiation (RNI) improve outcomes for patients at high risk of locoregional recurrence (LRR). Node-negative patients with the triple-negative (TN) subtype and those who do not have a pCR with neoadjuvant chemotherapy (NAC) are at increased risk for LRR, but whether the absolute risk for LRR is high enough to justify PMRT/RNI is uncertain. Patients with cT1-T3N0 and pN0 disease treated with NAC who had residual disease in the breast were identified from a prospective database. Patients were eligible for the study if they had mastectomy or breast-conserving therapy with negative margins and whole-breast radiation. Those receiving PMRT or RNI were excluded. Actuarial rates were estimated using the cumulative incidence function. The 227 patients in this study had a mean age was 51.4 ± 12.6years, and 82 (36.1%) were TN. During a median follow-up period of 35months, nine LRR events occurred. The overall crude and actuarial 3-year LRR rates were 4.4% and 5.9%, respectively. The crude LRR rate for the TN patients was 7.4%, and the 3-year actuarial rate was 10.1%. The hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) patients had a crude LRR rate of 2.8% and a 3-year actuarial rate of 3.2%. The HER2+ patients had a crude LRR rate of 2.7% and a 3-year actuarial rate of 3.3%. Locoregional recurrence is uncommon for patients with node-negative HR+/HER2- and HER2+tumors who have residual disease in the breast; however, TN patients have LRR rates that approach 10% at 3years, suggesting a possible role for PMRT/RNI for node-negative TN patients. Additional follow-up with more patients is needed for definitive conclusions.