The Efficacy and Toxicity of Hypofractionated Regional Nodal Irradiation in Breast Cancer Patients.

Abstract

Regional nodal irradiation (RNI) is increasingly used in place of axillary lymph node dissection (ALND) in carefully selected breast cancer patients. Although hypofractioned whole breast irradiation is standard for node-negative disease, long-term data on hypofractionated RNI (HF-RNI) are limited. This study aims to assess the long-term safety and effectiveness of HF-RNI for breast cancer patients. This retrospective analysis included 154 patients with node-positive or high-risk node-negative breast cancer treated with HF-RNI (>2 Gy/fraction) between 2008 and 2020. Median dose was 40 Gy/16 fractions to the breast, chest wall, or reconstructed breast as well as regional nodes. The primary endpoint was the incidence of chronic toxicity. Secondary endpoints were acute toxicity, local recurrence-free survival (LRFS), regional recurrence-free survival (RRFS), disease-free survival (DFS), and overall survival (OS). Acute toxicities were defined as those occurring during radiation therapy or within 90 days post-treatment; chronic toxicities were defined as those persisting or arising at least 180 days after radiation completion. Median follow-up was 65.4 months (range, 4-170 months). Median age was 58 years (interquartile range, 48.3-71.0). Sentinel lymph node biopsy was performed in 49.4% of patients, 47.4% underwent ALND, and 3.2% had no axillary surgery. RNI targets included supraclavicular and axillary level 1 to 3 nodes in 65.6% of patients, whereas 34.4% were treated only to the supraclavicular and level 3 nodes. There were 7 (4.7%) patients that had internal mammary nodes treated. Chronic brachial plexopathy occurred in 2.0% of patients, limited range of motion in 1.3%, and upper extremity lymphedema in 10.5%. Late cardiac and lung toxicity rates were low at 0.7% and 3.3%, respectively. Five-year actuarial rates of LRFS, RRFS, DFS, and OS were 98.0%, 99.3%, 90.1%, and 88.1%, respectively. HF-RNI demonstrates low rates of chronic toxicity and excellent disease control, supporting wider adoption in clinical practice. Long-term results of randomized trials of HF-RNI are needed for definitive evidence.