B7H1 expression and association with clinical response to sunitinib therapy in patients with metastatic renal cell carcinoma (mRCC).

416 Background: Preliminary data support that B7H1 expression is associated with objective response (OR) to anti-PD-1 antibody treatment in multiple solid tumors. The aim of this study was to retrospectively evaluate a possible association between B7H1 expression and clinical response to sunitinib therapy in mRCC patients. Methods: mRCC patients receiving sunitinib therapy (50mg 4/2) were identified and data regarding patient characteristics and clinical outcome to sunitinib were recorded. Immunohistochemistry (IHC) staining of B7H1 was done on pretreatment formalin fixed paraffin embedded (FFPE) tissue sections according to available protocol at Hopkins. IHC scorings were done by 2 independent pathologists who were blinded to outcomes and a 3 rd pathologist was used if there was a discrepancy between the first 2. Association of B7H1 expression with OR was assessed using Fisher’s exact test. Progression free survivals (PFS) were estimated using the Kaplan-Meier method and compared using log-rank test. Multivariate analyses were performed using logistic regression and Cox regression. Results: 20 cases were identified of which 18 had available FFPE for IHC analysis. 78% were male; median age was 55 (range 35-79); 72% ECOG PS of 0; 94% had prior nephrectomy; 89% were therapy naïve. 50% were intermediate risk category according to Heng criteria and the rest were poor risk. 55.6% (10/18) were positive for B7H1 expression (>5% positive cell membranous staining). 30% of B7H1 positive patients had OR whereas 50% of B7H1 negative patients had OR (p = 0.63). Median PFS were 19.3 and 6.2 mos for B7H1 negative and positive groups, respectively (p = 0.56). In multivariate models, B7H1 expression was neither associated with OR (odds ratio = 0.54, 95% CI = 0.07-4.23, p = 0.56) nor PFS (hazard ratio =1.06, 95% CI = 0.34-3.34, p = 0.92) after adjusting for Heng risk classification. Conclusions: In this study, B7H1 expression was not associated with clinical outcome to sunitinib therapy in metastatic RCC patients.