Ultra-Hypofractionated vs. Hypofractionated Radiation for Node-Positive Breast Cancer

In breast cancer patients with nodal involvement, numerous studies have demonstrated that adjuvant radiation therapy reduces the risk of local recurrence, regional recurrence, and distant metastases, in addition to improving survival. The dose and fractionation for adjuvant breast radiation therapy has evolved over time, as novel schedules have been compared to the current standard of care. Hypofractionated radiation therapy (266 cGy per fraction x 15-16 fractions over 3 weeks) has been shown to result in equivalent oncologic outcomes, as well as equivalent acute and late toxicity, when compared to standard fractionation (200 cGy per fraction x 25 fractions over 5 weeks). Subsequently, hypofractionated breast radiation has become the current standard of care. More recently, ultra-hypofractionated breast radiation (520 cGy per fraction x 5 fractions over 1 week) was shown in a randomized trial to be non-inferior to hypofractionated radiation when treating the breast after lumpectomy. However, the efficacy and toxicity of using ultra-hypofractionated radiation therapy when also treating the regional nodes has not been reported. This is important, as there is greater radiation exposure to several normal tissues, such as the arm/shoulder, brachial plexus, normal lymphatics, heart, and lung, when treating the regional nodes. In this randomized study, the investigators aim to compare the tolerability and efficacy of ultra-hypofractionated breast/chest wall and regional nodal radiation (SWIFT RT) against hypofractionated radiation (RT). The investigators will evaluate acute and late toxicity, oncologic outcomes (including local recurrence, regional recurrence, distant metastasis, and overall survival), cosmesis, and patient-reported quality of life. The investigators will collect blood samples for correlative studies of biomarkers of fibrosis and cardiac toxicity.