Grant: Project Grant

Studies have shown that radiotherapy to the chest wall and regional nodes following mastectomy and radiotherapy to regional nodes after breast conserving surgery reduces the risk of recurrence and breast cancer mortality in women with node positive breast cancer. While these benefits are important, it is recognized that there is a large group of patients with node positive breast cancer who are unlikely to recur or benefit from radiotherapy. Biomarkers are increasingly used to identify breast cancers that are likely to recur or respond to treatment. The luminal A breast cancer subtype has a low risk of recurrence and is less likely to respond to chemotherapy. Recent evidence from MA.20 a randomized trial of radiotherapy to the regional nodes supports that such cancers were less likely to respond to radiotherapy. This suggests that regional radiotherapy may not be necessary in patients with node positive luminal A breast cancer. The objective of this study is to determine if radiotherapy to the chest wall and regional lymph nodes following mastectomy or radiotherapy to the regional nodes following breast conserving surgery can be safely omitted in women with 1-3 positive axillary lymph nodes and luminal A cancer. An international multicentre randomized trial will be performed. Patients treated by mastectomy will be randomized to radiotherapy to the chest wall and regional nodes or not. Patients treated by breast conserving surgery will be randomized to radiotherapy to regional nodes or not. Radiation following surgery is associated with significant short-term and long-term side effects. The luminal A subtype of breast cancer accounts for up to 40% of patients with node positive breast cancer. If regional radiotherapy could be avoided in this group of patients it would have substantial benefits not only for women with breast cancer and their families, but the health care system at large.