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

Purpose: 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.

Methods and materials: 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.

Results: 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.

Conclusions: 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.