Objective: To investigate the utility of tumour carbonic anhydrase IX (CAIX) expression and histological features for predicting the outcome in patients with metastatic clear-cell renal cell carcinoma (mRCC) treated with vascular endothelial growth factor (VEGF)-targeted therapy.
Patients and methods: We identified 118 patients with mRCC initiating first-line VEGF-targeted therapy, including 94 with clinical and histological data, and available tissue. The primary endpoint was to detect an interaction between sorafenib vs sunitinib treatment and CAIX status on tumour shrinkage. Other treatment outcomes were also assessed.
Results: There was heterogeneity in tumour responsiveness to sunitinib or sorafenib according to CAIX status; the mean shrinkage was -17% vs -25% for sunitinib-treated patients with high vs low tumour CAIX expression, compared to -13% vs +9% for sorafenib-treated patients (P interaction, 0.05). A higher tumour clear-cell component was independently associated with greater tumour shrinkage (P= 0.02), response (P= 0.02) and treatment duration (P= 0.02).
Conclusions: Although CAIX expression had no prognostic value in patients with clear-cell mRCC treated with VEGF-targeted therapy, it might be a predictive biomarker for response to sorafenib treatment. Patients with a higher clear-cell component in their tumours are likely to have a superior clinical benefit from VEGF-targeted therapy.