HYPofractionated Adjuvant RadioTherapy in 1 Versus 2 Weeks in High-Risk Patients With Breast Cancer (HYPART): Acute Toxicity Results.

[PURPOSE] The HYPofractionated Adjuvant RadioTherapy study aimed to compare a 1-week adjuvant radiation therapy (RT) schedule with a 2-week schedule in high-risk patients with breast cancer. Here we present the acute toxicity data of the study.

[METHODS AND MATERIALS] The HYPofractionated Adjuvant RadioTherapy study was approved by the institutional ethics committee and was registered with ClinicalTrials.gov ID NCT04472845 and CTRI with REF/2020/09/037050. Patients with high-risk breast cancer after mastectomy or breast conserving surgery were randomized to receive an RT dose of 26 Gy in 5 fractions over 1 week or 34 Gy in 10 fractions over 2 weeks. Patients who underwent breast conserving surgery received a sequential or simultaneous integrated boost with a dose of 8 Gy/2#/2 days. Patients were planned and treated with a 2-dimensional or 3-dimensional technique. Acute radiation toxicities were assessed according to the Radiation Therapy Oncology Group grading system.

[RESULTS] A total of 941 patients treated between October 2020 and June 2024 were included in this analysis. Acute toxicity grade 0, 1, 2, and 3 with 1 week and 2 week schedules were observed in 265 (55%) versus 248 (54%), 141 (29.3%) versus 155 (33.8%), 73 (15.1%) versus 54 (11.8%), and 3 (0.6%) versus 2 (0.4%) patients (P = .282), respectively. Dysphagia was reported as grade 0, 1, and 2 in 461 (95.6%) versus 413 (90%), 14 (2.9%) versus 41 (8.9%), and 7 (1.5%) versus 5 (1.1%) patients with a 1-week and 2-week schedule (P = .001), respectively. Grade 1 and 2 arm pain was observed in 8 (1.6%) versus 8 (1.7%) and 7 (1.5%) versus 4 (0.9%) patients with a 1-week and 2-week schedule (P = .753), respectively. Acute arm edema was grade 1 and 2 in 100 (20.8%) versus 81 (17.6%), and 20 (4.1%) versus 28 (6.1%) patients in the 1-week and 2-week schedule (P = .227), respectively. Grade 1 and 2 cough was reported in 5 (1.0%) versus 2 (0.4%) and 4 (0.8%) versus 3 (0.7%) patients in the 1-week and 2-week schedule (P = .700), respectively.

[CONCLUSIONS] Dysphagia was less with the 1-week RT schedule as compared to the 2-week schedule. The trial showed the safety and tolerability of a 1-week regional nodal irradiation course and provided toxicity rates that will help future studies in sample size calculations.