Prognostic and predictive values of carbonic anhydrase IX (CAIX) and pathologic features in patients with metastatic clear cell renal cell carcinoma receiving targeted therapy

Abstract

e16067 Background: Tumor Carbonic Anhydrase IX (CAIX) expression and histologic features can predict outcome in patients with metastatic renal cell carcinoma (mRCC) treated with immunotherapy. We sought to investigate the prognostic and predictive utility of such features in patients receiving VEGF-targeted therapy. Methods: We identified 118 patients with mRCC initiating first- line VEGF-targeted therapy including 94 with clinical data, clear cell histology and available tissue. Tumors were evaluated for specific histologic features and for CAIX expression by immunohistochemistry using the MN75 antibody. The relationship between these pathology findings and tumor shrinkage and other treatment outcomes was assessed. Results: Higher tumor clear cell component was independently associated with greater tumor shrinkage (p=0.02), response (p=0.02) and treatment duration (p=0.02). Patients with high vs. low tumor CAIX expression had mean tumor shrinkages of -12% vs. -5%, respectively (p=.38). There was heterogeneity in tumor responsiveness to sunitinib or sorafenib according to CAIX status (p=0.055 for interaction): mean shrinkage was -17% vs. -25% (mean difference +8%, 95% CI -14% to +31%) for sunitinib-treated patients with high vs. low tumor CAIX expression compared to -13% vs. +9% (mean difference -22%, 95% CI -42% to -1%) for sorafenib-treated patients. Conclusions: Patients with higher clear cell component in their tumors are likely to experience superior clinical benefit from VEGF-targeted therapy. Although CAIX expression was not found to be of prognostic value in patients with clear cell mRCC treated with VEGF-targeted therapy, it may be a predictive biomarker for response to sorafenib treatment. [Table: see text]