SPARC microenvironment signature (SMS) in patients treated with nab-paclitaxel (nabP)/carboplatin (C)/bevacizumab(B) for triple-negative metastatic breast cancer (TNMBC).

e21040 Background: SPARC is an albumin-binding protein associated with poor prognosis that may mediate intratumoral accumulation of nab-P. SPARC is associated with both tumor cells and stromal components. We examined SMS in paired primary (P) and metastatic (M) TNBC biopsies (bxs) to 1) determine changes in expression, and 2) examine potential correlations with response to therapy with nab-P/C/B. Methods: First- and second-line TNMBC pts (n = 27) received nabP (100 mg/m2) and C (AUC = 2) on d1,8,15 of a 28 d cycle. B (10 mg/kg) was given on d1, 15. Paraffin- embedded P and M bxs were required (first line). PFS, ORR, and CBR were determined. Tumor SMS was determined using a validated SPARC IHC method. Scoring included: % cells stained in each field, intensity of staining, and overall score. Multivariable IHC data were analyzed using GeneSpring and Nexus analysis programs. Results: SMS data were available for 20 pts. SMS of M bx distinguished a low risk (n= 5, PFS = 16.0 mos) from a high risk group (n = 15,...