DEBRA Study is a Phase III trial to see if surgery and hormone treatment alone work as well as adding radiation after breast-conserving surgery for certain breast cancer patients. Breast-conserving therapy often includes radiation to prevent cancer from coming back. But, radiation can be burdensome. This study will see if it can be safely skipped for patients with hormone-sensitive and HER2-negative breast cancer that have low risk of recurrence. HER2-negative means the cancer cells do not have a protein called HER2 on their surface, and hormone-sensitive means the cancer grows in response to hormones like estrogen or progesterone.

• This study is for patients who have completed surgery, not started hormone therapy, and have a recurrence score of 18 or less.
• The study needs patients to agree to hormone therapy for at least 5 years.
• It's important to have no signs of cancer spreading elsewhere in the body before joining.