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

Women with invasive carcinoma of the breast with negative axillary nodes or DCIS, following BCS and/or chemotherapy, who meet the inclusion criteria will be screened and approached for eligibility assessment and potential study enrollment. All potentially eligible and consenting patients who do not meet the exclusion criteria will have a Computed Tomography (CT) simulation of the ipsilateral breast prior to randomization. All cases will be required to be planned prior to the randomization to ensure that dosimetric coverage and normal tissue restrictions can be met. If the seroma is not clearly visible or if the surgical clips do not adequately identify a previous surgical cavity, the patient will not be eligible for randomization. Eligible, consenting patients will be randomly allocated to receive radiotherapy of 3DCRT APBI 30Gy 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 using the EORTC Breast Cosmetic Rating System. Radiation toxicity will be assessed using the NCI CTCAE version 4.02. The primary outcome is adverse cosmetic outcome at 2 years. The trial will be conducted in clinical centres within Canada.