Survival determinants and toxicity of second-course radiotherapy for isolated nodal recurrences in breast cancer.

Abstract

Background: Isolated nodal recurrence (INR) after localized breast cancer is rare, with an incidence of less than 1%. Curative management typically includes surgical resection, often with axillary lymph node dissection (ALND), followed by regional nodal radiotherapy. However, evidence-based guidelines remain limited due to the rarity of this clinical scenario. The aim of this study was to evaluate survival determinants and the acute and long-term toxicities associated with second-course regional nodal irradiation as part of curative strategies for INR after localized breast cancer.

Materials and methods: This retrospective study included 11 patients with localized breast cancer who developed ipsilateral, nonmetastatic INR between 2003 and 2019. All patients were treated with curative intent, including regional nodal irradiation. Overall survival (OS), cancer-specific survival (CSS), metastasis-free survival (MFS), local control, and treatment toxicities were analyzed. Survival probabilities were calculated using the Kaplan-Meier method, and Cox regression was used to assess prognostic factors.

Results: The 5‑year OS and CSS were 71.6%, while MFS was 62.3%. Inclusion of internal mammary chain (IMC) irradiation significantly improved OS, CSS, and MFS (p < 0.01). Triple-negative breast cancer (TNBC) INRs were associated with worse survival outcomes. Acute grade 2 toxicities included radiodermatitis (36.4%), and late grade 2 toxicities were limited to fibrosis (18.2%). No cardiac, pulmonary, or grade 3 or higher toxicities were reported.

Conclusion: This study highlights the favorable survival outcomes and safety profile of contemporary curative strategies for INRs following localized breast cancer, with a 5-year OS rate exceeding historical benchmarks. Internal mammary chain irradiation appears to improve survival without increased toxicity. However, the poor prognosis associated with TNBC INR underscores the need for effective systemic therapies. Prospective multicenter trials are essential to validate these findings and optimize treatment protocols.