RAPID: Randomized Trial of Accelerated Partial Breast Irradiation

To determine if Accelerated Partial Breast Irradiation, using 3D CRT, is as effective as Whole Breast Irradiation following breast conserving surgery in women with an new histological diagnosis of ductal carcinoma in situ only or invasive breast cancer without evidence of metastatic disease. Effectiveness will be determined by the rate of ipsilateral breast tumour recurrence. General objective is to improve the convenience and quality of life of female patients who receive breast irradiation.

Following breast conserving surgery or on completion of chemotherapy, patients will be stratified according to age, tumour histology, tumour size, adjuvant hormonal therapy and clinical centre. Patients will be allocated to receive either whole breast irradiation or 3D CRT accelerated partial breast irradiation. Radiation therapy will be administered as soon as possible following the healing of the surgical incision (3-4 weeks) and within 12 weeks if the patient is not treated with chemotherapy. If the patient is treated with chemotherapy, radiation therapy will begin after 2 weeks and not beyond 8 weeks after the last dose of chemotherapy. Patients treated with whole breast irradiation will receive a total dose of 42.5 Gy in 16 fractions, given on a daily basis, over a time period of 22 days. Patients with large breast size are permitted to receive a total dose of 50 Gy in 25 fractions, given on a daily basis, over a time period of 35 days. Boost irradiation is permitted in patients treated with whole breast irradiation. Boost irradiation of 10 Gy/4-5 fractions daily over a time period of 4-7 days is permitted for patients deemed at moderate to high risk of local recurrence as per local cancer centre guidelines. Patients treated with 3D CRT accelerated partial breast irradiation will receive a total dose of 38.5 Gy in 10 fractions, delivered twice a day, over a time period of 5-8 days. Each daily dose must be separated by 6-8 hours. Patients will be followed indefinitely and assessed formally at 6 and 12 months after the date of randomization and then on a yearly basis. Patients will be assessed for acute and late radiation toxicity, cardiac toxicity, recurrent disease, new primary cancer, cosmetic outcome, quality of life and overall survival.