Darby

Researchers are evaluating whether breast conservation surgery combined with endocrine therapy can achieve a similar rate of invasive or non-invasive ipsilateral breast tumor recurrence (IBTR) compared to breast conservation surgery followed by breast radiation and endocrine therapy in patients with Stage I, hormone sensitive, HER2-negative breast cancer with an Oncotype recurrence score of 18 or less. This Phase III trial builds on the established role of radiation after lumpectomy, aiming to identify if radiation can be safely omitted in certain low-risk patients to reduce treatment burden and side effects. Participants receive either breast radiation plus endocrine therapy or endocrine therapy alone. Radiation therapy involves external beam radiation to the whole breast with or without a boost, partial breast irradiation, or accelerated partial breast irradiation, starting within 12 weeks after the last breast surgery. Endocrine therapy is given for a minimum of 5 years, with the specific drug choice and schedule determined by the treating physician. Endocrine therapy may begin before, during, or after radiation therapy, depending on the treatment group. Throughout the study, participants undergo regular assessments including imaging such as mammograms or MRI within six months before enrollment, and clinical evaluations to monitor tumor recurrence. The main outcome measured is the time to invasive or non-invasive ipsilateral breast tumor recurrence over five years. Safety, adherence to therapy, and recovery from surgery are also monitored. The total participation period includes at least five years to evaluate long-term recurrence rates.