HYPofractionated Adjuvant RadioTherapy in 1 versus 2 weeks in high-risk patients with breast cancer (HYPART): a non-inferiority, open-label, phase III randomised trial

Background Breast cancer is the most common cancer in women. Radiotherapy is an important part of breast cancer treatment after surgery. Breast cancer radiotherapy is usually delivered in 3–5 weeks. This is a long duration for women with breast cancer to stay away from the family and work. We wanted to reduce this duration so that the wages loss and the logistics can be minimised for these patients. Hypofractionation, i.e. high dose per fraction, is delivered in a smaller number of days. In this study, we will compare a 1-week schedule of hypofractionated adjuvant whole breast/chest wall and/or regional nodal radiotherapy against 2 weeks for locoregional disease control, toxicities, quality of life (QoL), survival and second cancers after primary surgery in patients with breast cancer. Methods Eligible patients with breast cancer after mastectomy or breast conserving surgery (BCS) will be treated with a radiotherapy dose of 26 Gy in 5 fractions over 1 week in the study arm and 34 Gy in 10 fractions over 2 weeks in the control arm. The primary endpoint of this noninferiority study will be locoregional tumour control. Secondary endpoints will be early and late radiation toxicities, quality of life, contralateral primary tumours, regional and distant metastases, survival and second cancers. A total of 1018 patients will be randomised (1:1) to receive 1 week or 2 weeks of radiotherapy. An event-driven analysis will be performed after at least 94 patients have documented locoregional recurrences. Acute radiation toxicity will be assessed and scaled according to the RTOG grading system. Late radiation toxicity will be assessed with the Radiation Therapy Oncology Group and the European Organisation for Research and Treatment of Cancer late radiation morbidity scale. Cosmetic assessment will be done using Harvard/NSABP/RTOG breast cosmesis grading scale at baseline and 3 and 5 years. QoL will be assessed with EORTC QLQ-30 and EORTC QLQ-BR 23 at baseline and 3 and 5 years. Discussion Hypofractionation reduces treatment time to half while maintaining breast cosmesis and gives control rates equal to conventional fractionation. This is possible because breast tissue can tolerate high dose per fraction. In this study, we presume that 1-week radiotherapy will be non-inferior to 2 week radiotherapy, i.e. disease control will be similar with both the schedules without additional side effects, and QoL of these patients will be maintained. If we are able to achieve these outcomes, then patients will be able to complete their radiotherapy in less duration. There is not much data on regional nodal irradiation with hypofraction in breast cancer. We have used hypofraction for regional nodal irradiation in the past and not encountered any safety issue. If we are able to prove that late-term effects are comparable in the two schedules, it will make the radiation oncologist confident about hypofractionation in breast cancer. As breast cancer is a leading cancer in females and radiation therapy is an integral part of its local management, hypofractionation will help radiation centres worldwide to meet the growing need for radiation treatment in breast cancer, particularly in developing countries where resources are limited. It will also reduce the financial burden on the patient and family. Since we will treat these patients with both simple and complex radiotherapy techniques, it will also be possible for the low-income countries to follow this trial without needing a high-end or expensive radiotherapy equipment as the planning and treatment process will be very simple. Trial registration The trial is registered with ClinicalTrials.gov ID NCT04472845 and CTRI with REF/2020/09/037050.