Neoadjuvant Talazoparib (Tala) For Operable Breast Cancer Patients With A Brca Mutation (Brca Plus ).

508Background: TALA has demonstrated efficacy in patients (pts) with BRCA+ metastatic breast cancer. We previously reported a window trial with median 88% tumor volume reduction after 2 months for early stage breast cancer. This study expanded to evaluate the pathologic response of TALA alone x 6 months in BRCA+ pts and operable breast cancer. Methods: The study was approved by the Institutional Review Board. Eligibility included ≥ 1 cm tumor and BRCA+. HER2+ tumors were excluded. Twenty pts underwent a pre-treatment biopsy, 6 months of once daily oral TALA (1 mg), followed by definitive surgery. Pts received adjuvant therapy at physician’s discretion. Endpoint was residual cancer burden (RCB). With 20 patients, the RCB0 + RCB1 response rate can be estimated with a 95% confidence interval with half width u003c 20%. Results: All 20 planned pts have enrolled from 08/2016-09/2017: median age = 38 (range 23-58); BRCA1+ = 16 and BRCA2+ = 4; 17 patients had triple negative breast cancer (TNBC, ER/PR u003c 10%) and 3 ha...