Phase II trial evaluating the use of 21-gene recurrence score (RS) to select preoperative therapy in hormone receptor (HR)-positive breast cancer.

562 Background: Hormone receptor (HR)- positive breast cancer patients (pts) typically have lower pathological responses to pre-operative chemotherapy than HR-negative breast cancers. Objective: We evaluated the pathologic and radiologic response rates to pre-operative endocrine therapy or chemotherapy, as directed by RS, in pts with HR-positive resectable breast cancers. Methods: Pts with HR-positive breast cancers had RS performed on the initial diagnostic biopsy. Pts were treated pre-operatively as follows based on RS: ≤10, exemestane +/- goserelin for 6 to 12 months (ET); 11 to 25 randomized to ET or docetaxel-cyclophosphamide (TC) for 6 cycles (CT); ≥ 26, CT. Results: From 4/2009 to 12/2012, 66 pts signed consent for RS testing and 46 are evaluable for efficacy analysis. Median age is 57 (40 to 78); one-third of pts are African-American; 41% have clinically node positive disease. RS ranged from 2 to 57. 28 pts received CT: Pathologic complete response (PCR) rate was 10% and 60% of cancers were down-s...