Resource-sparing Post-mastectomy Radiotherapy in Breast Cancer

Post-mastectomy radiotherapy (PMRT) substantially reduces the risk of loco- regional failure as shown in several studies and meta-analyses. Two large trials for pre-menopausal node-positive breast cancer patients treated with mastectomy and chemotherapy showed that PMRT not only reduced loco- regional failure rates but also improved disease-free and overall survival rates. Although the benefit of PMRT is clear, the optimal volume of tissues to be covered by the radiotherapy fields is controversial. Since the chest wall is the most likely location of recurrence, there is uniform consensus that the chest wall should be irradiated. However, areas of controversy exist regarding irradiation of the regional lymph nodes (axillary, supraclavicular and internal mammary lymph nodes), optimal radiation dose, and dose-fractionation. If equivalent results could be achieved by omitting irradiation of the supraclavicular region in patients receiving adjuvant systemic therapy, this will simplify and expedite treatment in this patient population. Furthermore, the use of a shortened fractionation schedule of 40 Gy in 15 fractions (2.67 Gy per fraction) over 3 weeks which has been used in the UK and Canada for post-mastectomy patients for several decades will shorten the duration of treatment by reducing the number of patient visits for radiotherapy and increase the number of patients who can be treated. Treatment will be more convenient for patients and a reduction in the number of treatments could result in savings for strained health care systems. This is a randomized comparison of two different radiotherapy field set-ups for post-mastectomy treatment of locally advanced breast cancer. Patients who have undergone modified radical mastectomy including axillary lymph node dissection will be randomized to receive one of two radiotherapy treatment arms, A and B following the completion of adjuvant chemotherapy. The radiotherapy for treatment Arm A consists of irradiation of the chest wall only while Treatment Arm B includes irradiation of the chest wall and the ipsilateral supraclavicular field. Patients on both treatment arms will receive radiation with a shortened fractionation schedule. Patients will be evaluated for local control, regional control, survival and treatment toxicity.