Impact of combining PgR score and original preoperative endocrine prognostic index (PEPI) score as a prognostic factor of neoadjuvant endocrine therapy using exemestane in postmenopausal ER-positive/HER2-negative breast cancer.

548 Background: Neoadjuvant endocrine therapies (NAE) using aromatase inhibitors effectively reduce tumor size in postmenopausal ER-positive breast cancer (BC). The utility of PEPI scoring in predicting of the recurrence-free survival (RFS) after NAE is well-known. On the other hand, PgR can be a prognostic factor of ER-positive BC. We compared original PEPI score with PgR status alone, and modified PEPI score including PgR status, as prognostic factors of NAE in postmenopausal ER-positive/HER2-negative BC. Methods: Our study included 107 Japanese women with invasive ER-positive/HER2-negative BC who were received NAE with exemestane (25 mg/day) for at least 4 months (median follow-up: 47 months). Analysis 1: PEPI score (0-12 points) of each patient was determined using ypT, ypN, Ki67 and ER (Allred score), and patients were divided into 3 risk groups: low (0), moderate (1-3), and high ( ≥ 4). RFS and cancer-specific survival (CSS) were compared between groups. Analysis 2: Cutoff values of PgR were tentati...