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

Background: 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.

Methods: 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.

Results: The 227 patients in this study had a mean age was 51.4 ± 12.6 years, and 82 (36.1%) were TN. During a median follow-up period of 35 months, 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%.

Conclusions: 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 3 years, suggesting a possible role for PMRT/RNI for node-negative TN patients. Additional follow-up with more patients is needed for definitive conclusions.