Hypofractionated Regional Nodal Irradiation in Breast Cancer: Initial Results of a Prospective Clinical Trial

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Conference Proceeding

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International Journal of Radiation Oncology Biology Physics



Randomized clinical trials have validated the efficacy and safety of hypofractionated whole breast irradiation (HWBI) in patients with early-stage breast cancer. Toxicities associated with hypofractionated treatment in patients requiring regional nodal irradiation are less well described, and the utilization of hypofractionation in these patients is uncommon in the United States. We report an interim analysis of acute toxicity of a prospective trial of hypofractionated regional nodal irritation (H-RNI).


This is a prospective, single-arm trial at a single institution. Eligible patients comprised those with locally advanced, non-metastatic breast cancer and required adjuvant radiation therapy to the regional lymphatics in addition to the breast or chest wall. Patients were stratified into two groups based on extent of axillary surgery: ≤ 5 lymph nodes (Group 1) and > 5 lymph nodes removed (Group 2). We enrolled 31 patients (23 in Group 1, 8 in Group 2) from 11/2018 to 12/2021. Patients received a dose of 42.56 Gy in 16 fractions to the breast/chest wall and regional lymphatics with a sequential boost of 10-12.5 Gy in 4-5 fractions to the surgical cavity or mastectomy scar. Circumferential arm measurements at 10 cm intervals were taken at baseline and predefined intervals following treatment. The primary endpoint is clinically significant lymphedema, defined as a ≥ 10% difference in ipsilateral arm, forearm, or both, compared to the contralateral side. Additional toxicities were assessed using the Common Terminology Criteria for Adverse Events (CTCAE) criteria.


The median follow up was 19 months and the median age was 59 years. Acute lymphedema and CTCAE toxicities were analyzed in 27 and 31 patients, respectively. One patient (3.2%) in Group 2 met the predetermined criteria for clinically significant lymphedema. One patient experienced symptomatic lymphedema, requiring a compression sleeve. However, her measurements did not meet the threshold for clinically significant lymphedema. The most prevalent Grade 1 toxicities were hyperpigmentation (66.7%), fatigue (66.7%), breast pain (63.3%), and radiation dermatitis (63.3%). The most prevalent Grade 2 toxicities were radiation dermatitis (26.7%) and hyperpigmentation (20%). The incidence of any ≥ Grade 3 toxicity was 6.5% (n=2) related to hyperpigmentation. One patient (3.2%) developed grade 2 pneumonitis. All cosmetic outcomes were rated as good or excellent at 3 months. There were no grade 4 or 5 toxicities.


Our preliminary data suggest that H-RNI is well tolerated. The rates of acute lymphedema and acute toxicity were very low. A matched comparison with patients treated with conventionally fractionated RNI at our institution is ongoing.




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American Society for Radiation Oncology (ASTRO) Annual Meeting, October 23-26, 2022, San Antonio, TX.