Toxicity and Efficacy of Hypofractionated Regional Nodal Irradiation

Abstract

Hypofractionated whole-breast irradiation (HF-WBI) has been widely adopted. However, there are still limited data on whether hypofractionated regional nodal irradiation (HF-RNI) is safe and effective. We report toxicity and cancer outcomes with our HF-RNI approach. This retrospective study included 154 patients with node-positive or high-risk node-negative breast cancer treated with HF-RNI with curative intent at a single academic institution from 2008-2020. Median dose to the breast or chest wall/reconstructed breast was 40 Gy in 16 fractions (interquartile range [IQR], 40-45 Gy in 16-18 fractions). Median dose to the regional nodes was 40 Gy in 16 fractions (IQR, 40-40 Gy in 16-16 fractions). The primary end-point was the rate of chronic toxicity. Secondary endpoints were local recurrence-free survival (LRFS), regional recurrence-free survival (RRFS), disease-free survival (DFS), and overall survival (OS). Toxicities were scored using the Common Terminology Criteria for Adverse Events v5.0 and Radiation Therapy Oncology Group scale where appropriate. This study was approved by the Institutional Review Board. Median follow-up was 46 months (IQR 33-63 mo). Median age at diagnosis was 58 years. Sentinel lymph node biopsy (SLNB) was performed in 49% of patients, 16% underwent both SLNB and axillary lymph node dissection (ALND), 32% underwent ALND alone, and 3% had no axillary surgery; 79% had partial mastectomy and 21% had total mastectomy with or without reconstruction. The nodal target included the supraclavicular and axillary Level 1-3 nodes in 66% of patients and supraclavicular and Level 3 nodes in 34%. The crude incidence of grade 1 chronic brachial plexopathy was 2%, grade 1 chronic limited range of motion (LROM) of the upper extremity was 3%, and chronic upper extremity lymphedema was 8% (11 patients with grade 1 toxicity and 1 patient with grade 2 toxicity). The only grade 3+ chronic toxicity was hyperpigmentation (1%). The median time to the development of the highest-grade toxicity was 10 months for brachial plexopathy, 10 months for LROM, and 11 months for lymphedema, respectively. Five-year actuarial rates of LRFS, RRFS, DFS, and OS were 98%, 99%, 90%, and 88%, respectively. HF-RNI resulted in low rates of chronic toxicities and excellent disease control in this study. Results of randomized trials of HF-RNI are needed for definitive evidence, but these retrospective data support wider adoption of HF-RNI.