TPS590 Background: Following neoadjuvant chemotherapy (NACT), patients (pts) with triple negative breast cancer (TNBC) achieving pathologic complete response/residual cancer burden-0 (pCR/RCB-0) or minimal residual disease (RCB-I) have an improved relapse free survival when compared to pts with more extensive residual disease (RCB-II/III) (Symmans et al, JCO 2017). Pts with chemo-resistant TNBC have a poor prognosis as there are currently no FDA-approved targeted agents available for TNBC. We previously reported the ability of a novel gene expression signature (GES) to predict sensitivity to NACT (Hatzis et al, JAMA 2011). Here we seek to prospectively validate the use of this GES in combination with imaging to predict response to NACT and establish the clinical impact of selecting pts predicted to have non-responsive disease (NRD) for enrollment in clinical trials of targeted therapy. Methods: All pts will undergo a biopsy of the primary tumor for molecular characterization (MC) and will be randomized 2:1 to know their MC results (intervention arm) or not (control arm). A maximum of 360 pts will be enrolled and randomized using a group sequential design with one-sided O’Brien-Fleming boundaries, with two equally spaced binding interim tests for futility and superiority and one final test, having an overall Type I error of 0.05 and power of 0.80 to detect an improvement in pCR/RCB-I from 50% to 64%. Secondary endpoints include rates of clinical trial enrollment, disease free survival and integrated biomarker analyses. All pts will receive 4 cycles of anthracycline-based NACT with imaging done every 2 cycles to assess response. After completion or progression on anthracycline-based NACT, pts predicted to have NRD based on MC/imaging (intervention arm) or imaging alone (control arm) will be offered enrollment on a clinical trial. Pts are eligible if they have stage I-III TNBC with a primary tumor that is ≥1.5cm. Pts with contraindications to anthracyclines and/or taxanes are excluded. Enrollment began in November 2015. 105 pts have been enrolled to date with 71 and 34 pts randomized to the intervention and control arms, respectively. Clinical trial information: NCT02276443.