Pre-Operative Endocrine Therapy to Guide Radiation Decisions in Older Women With Early-Stage Breast Cancer (POWER II)

What this Trial Is About

Researchers are evaluating treatment options for women aged 65 and older with early-stage estrogen receptor positive (ER+) breast cancer. This Phase III, multisite study compares two groups: one receiving 3 months of pre-operative endocrine therapy (pre-ET) before breast-conserving surgery (BCS), and the other proceeding directly to surgery without pre-ET. The study aims to understand how pre-ET influences decisions about radiation therapy (RT) and endocrine therapy (ET) use, addressing concerns of over- and under-treatment in this population. Participants will be randomly assigned to either receive 90 days of pre-ET using tamoxifen or an aromatase inhibitor before surgery or to move directly to BCS as standard care. In both groups, the choice to omit or administer RT will be made by patients and their physicians. Although not required by the study, all patients may be recommended to take adjuvant ET as appropriate, with adherence monitored for two years. The study evaluates whether pre-ET affects treatment choices and tolerance to endocrine therapy. During the study, researchers will assess patient-reported outcomes such as tolerance and compliance with ET through surveys. The main outcomes measured at 24 months include the proportion of patients who omit RT and do not adhere to ET, and those treated with BCS plus RT and ET. Secondary assessments cover decision conflict, regret, quality of life, early side effects of ET, and long-term cancer outcomes over five years. Participants will be followed through surgery, treatment, and monitoring phases to track treatment adherence and cancer recurrence.

Pre-Operative Window of ET to Inform RT Decisions (POWER II)