Tailor RT: A Randomized Trial of Regional Radiotherapy in Biomarker Low Risk Node Positive Breast Cancer (CCTG MA.39)

The purpose of this study is to compare any good and bad effects of not giving regional radiotherapy to using regional radiotherapy. This study will help researchers learn if not giving regional radiotherapy is just as good as using regional radiotherapy. To be better, the approach of not giving regional radiotherapy should keep your breast cancer from coming back as good as giving regional radiotherapy. There will be about 2140 people taking part in this study.

Are you Eligible? (Inclusion Criteria)

• To be eligible for this study, subjects must:
• 1. be ≥ 40 years of age.
• 2. have been treated with Breast Conserving Surgery (BCS) or mastectomy
• 3. have Oncotype DX recurrence score <18% (will be tested if it has not been
• performed)
• 4. be estrogen receptor positive (greater than or equal to 1%) and HER2 negative
• 5. have had endocrine therapy initiated or planned for ≥ 5 years to be given
• concurrently or following RT.