Hypofractionated LocoRegional Radiotherapy in Breast Cancer

A multi-centre, randomized, non-inferior, phase III study comparing two radiation treatment modalities, conventional fractionation with hypofractionation for locoregional RT. Eligible, consenting patients with newly diagnosed and histologically confirmed invasive carcinoma of the breast without evidence of metastatic disease; treated with definitive surgery \[BCS or mastectomy with nodal staging using sentinel lymph node biopsy (SLNB) or axillary lymph node dissection (ALND)\] will be randomized in a 1:1 fashion to either conventional locoregional RT (control group) or hypofractionated locoregional RT (experimental group). Stratification factors include: body mass index, the performance of ALND, type of surgery (BCS or mastectomy) and clinical centre. Study participants will be assessed for lymphedema, the primary outcome, by measuring arm volume. Arm mobility will be assessed by measuring arm movement. Study participants will be assessed for acute and late radiation toxicities, during and post RT. Study participants will be followed and assessed annually for breast cancer recurrence (BCR), new second cancers, quality of life (QOL) and overall survival. Cost effectiveness and cost utility will also be determined. The planned sample size is 588 study participants. The study will be conducted at clinical centres throughout Canada.