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

Early-stage, estrogen receptor positive (ER+) breast cancer is traditionally treated with breast conserving surgery (BCS), radiation therapy (RT) and 5-10 years of adjuvant endocrine therapy (AET). Radiation therapy (RT) omission is an established treatment paradigm for women 65 years and older with ER+, node negative, small (≤ 3 cm) breast cancer. Despite the option for RT omission being recommended in the National Comprehensive Cancer Network (NCCN) guidelines, multiple modern studies demonstrate that a majority of older women still receive RT, raising concern for over-treatment. Conversely, there are a portion of patients who choose to omit RT but are not able to tolerate AET and thus are at risk for under-treatment and worse oncologic outcomes.

In the POWER I trial, patients were treated with 90 days of pre-operative endocrine therapy (pre-ET) as a window to establish endocrine therapy (ET) tolerance. The POWER I trial prospectively validated 90 days of pre-operative ET to determine if it could be used as a tool to inform adjuvant RT decisions and recommendations by patients and physicians respectively. Ninety days of pre-ET was shown to influence patient and physician preferences regarding adjuvant RT.

In the POWER II trial, participants will be randomized to treatment on either a) an intervention arm consisting of a 90-day window of pre-ET or b) the standard of care (control) arm in which participants proceed directly to BCS. In both arms, the decision to omit or administer adjuvant RT will be made by the treating physicians and patients. While not required per protocol, all patients will be recommended for AET if deemed appropriate by their oncologist, and adherence through 2 years will be monitored. The POWER I study revealed that pre-ET impacts patients' and physicians' decisions regarding adjuvant therapy and facilitates adjuvant therapy decisions that meld patient preferences and side effect tolerance. The purpose of the POWER II study is to examine whether 90 days of pre-ET results in a decrease in the number of (1) patients being treated with BCS alone and (2) patients treated with BCS+RT+AET. Adherence to AET will be defined as taking AET at 2 years post-BCS.

• Treatment with pre-ET and its impact on Decision Conflict [Срок оценки: 24 months]
• Treatment with pre-ET and its impact on Decision Regret [Срок оценки: 24 months]
• Assessing whether patient's final treatment correlates with their beliefs about breast cancer [Срок оценки: 7 months]
• Assessing whether patient's final treatment correlates with their beliefs about breast cancer [Срок оценки: 7 months]
• Assessing whether patient's final treatment correlates with their beliefs about breast cancer [Срок оценки: 7 months]
• Assessing whether treatment with pre-ET leads to improved Health Related Quality of Life compared to those treated with standard of care [Срок оценки: 24 months]
• Assessing whether early side effects of ET correlate with patient treatment group within study arms [Срок оценки: 24 months]
• Assessing whether early side effects of ET correlate with patient treatment group within study arms [Срок оценки: 24 months]
• To obtain data on local recurrence [Срок оценки: 5 years]
• To obtain data on regional recurrence [Срок оценки: 5 years]
• To obtain data on contralateral breast cancer [Срок оценки: 5 years]
• To obtain data on distant metastases [Срок оценки: 5 years]