Preliminary results of hypofractionated radiotherapy in breast cancer in Chandigarh, India: single-centre, non-inferiority, open-label, randomised, phase 3 trial

Background Globally, most of the randomised trials with hypofractionation in patients with breast cancer have used 3dimensional conformal radiotherapy technique (3D -CRT). As facilities for 3D -CRT technique may not be available in low -resource settings, there is a need to see if hypofractionation is feasible and safe with 2 -dimensional (2-D) technique. In this study, we compared a 3 -week radiation schedule with a 2 -week schedule of hypofractionated radiotherapy in patients with breast cancer with 2-D technique. Methods The current study was an open -label, randomised, phase 3 trial. Patients with breast cancer, stage I -III, post mastectomy or after breast conservative surgery who needed adjuvant locoregional radiotherapy were randomised in the Department of Radiotherapy & Oncology, Post Graduate Institute of Medical Education & Research (PGIMER), Chandigarh, India; to 34Gy in 10 fractions over 2 weeks (2 -week arm) or 35Gy in 15 fractions over 3 weeks to the chest wall and 40Gy/15#/3wks to breast and supraclavicular fossa (3 -week arm). Boost dose when indicated was 8 - 10Gy/2 - 4#/2 - 4 days in both the arms. Patients were planned on a 2 -dimensional (2D) simulator with 2 tangential fi elds to breast/chest wall and incident supraclavicular fossa fi eld. Acute toxicity was assessed using the Radiation Therapy Oncology Group (RTOG) grading scale. Assessments were carried out weekly during radiotherapy and at 4 weeks after treatment by the physician. Cosmetic outcome was assessed using the Harvard/ National Surgical Adjuvant Breast and Bowel Project (NSABP)/RTOG scale. The toxicity rates between the two arms were compared using Fisher ' s exact tests. The trial was approved by institutional ethics committee and registered with ClinicalTrials.gov, number NCT04075058. Findings This study included 1121 eligible patients from June 2015 to December 2020. Median follow-up was 35 months (6 - 84 months). Mean age was 48 years (24 - 75 years). The patient characteristics were comparable between the two arms except for more mastectomies in the 3 -week arm and more node -positive patients in the 2week arm. There were more oestrogen receptor -positive tumors in the 3 -week arm. Acute skin toxicities were comparable between the two arms. Grade 2 and 3 skin toxicity was 100 (18%) and 82 (15%); and 16 (3%) and 12 (2%) in the 3 -week and 2 -week arm (p = 0.21), respectively. Cosmetic outcome was assessed as Excellent or Good for 89% of patients in the 3 -week arm as compared to 94% in the 2 -week arm (p = 0.004). Interpretation The two radiation schedules were comparable in terms of acute skin toxicity. The cosmetic outcome was better with the 2 -week schedule. The preliminary fi ndings indicate 2 -week radiotherapy schedule with 2-D technique was better than the 3 -week schedule in patients with breast cancer. However, disease outcomes and late -term toxicities need to be further checked. Health Asia 2024;24: Published https://doi.org/10. 1016/j.lansea.2024. 100392