Trial of Radiation Fractionation Schedules for Once-a-Day Accelerated Partial Breast Irradiation

This is a multi-centre randomized phase II trial in women with invasive carcinoma of the breast with negative axillary nodes or Ductal Carcinoma In-situ (DCIS) treated by Breast Conserving Surgery (BCS). Eligible, consenting patients will be randomly allocated to receive radiotherapy of 3 Dimensional Conformal Radiation Therapy (3DCRT) Accelerated Partial Breast Irradiation (APBI) 30 Gray (Gy) in 5 daily fractions of 6Gy or 27.5Gy in 5 daily fractions of 5.5Gy over one week. Patients will be followed at 12, 24, 36 and 60 months post randomization. Cosmetic outcome will be measured using photographs and evaluated by a panel of trained radiation oncologists. Radiation toxicity will be assessed using National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE).