Results of a Multicenter Phase II Study of Atezolizumab and Bevacizumab for Patients With Metastatic Renal Cell Carcinoma With Variant Histology and/or Sarcomatoid Features

PURPOSE In this multicenter phase II trial, we evaluated atezolizumab combined with bevacizumab in patients with advanced renal cell carcinoma (RCC) with variant histology or any RCC histology with ≥ 20% sarcomatoid differentiation. PATIENTS AND METHODS Eligible patients may have received previous systemic therapy, excluding prior bevacizumab or checkpoint inhibitors. Patients underwent a baseline biopsy and received atezolizumab 1,200 mg and bevacizumab 15 mg/kg intravenously every 3 weeks. The primary end point was overall response rate (ORR) by RECIST version 1.1. Additional end points were progression-free survival (PFS), toxicity, biomarkers of response as determined by programmed death-ligand 1 (PD-L1) status, and on-therapy quality-of-life (QOL) metrics using the Functional Assessment of Cancer Therapy Kidney Symptom Index-19 and the Brief Fatigue Inventory. RESULTS Sixty patients received at least 1 dose of either study agent; the majority (65%) were treatment naïve. The ORR for the overall population was 33% and 50% in patients with clear cell RCC with sarcomatoid differentiation and 26% in patients with variant histology RCC. Median PFS was 8.3 months (95% CI, 5.7 to 10.9 months). PD-L1 status was available for 36 patients; 15 (42%) had ≥ 1% expression on tumor cells. ORR in PD-L1–positive patients was 60% (n = 9) v 19% (n = 4) in PD-L1–negative patients. Eight patients (13%) developed treatment-related grade 3 toxicities. There were no treatment-related grade 4-5 toxicities. QOL was maintained throughout therapy. CONCLUSION In this study, atezolizumab and bevacizumab demonstrated safety and resulted in objective responses in patients with variant histology RCC or RCC with ≥ 20% sarcomatoid differentiation. This regimen warrants additional exploration in patients with rare RCC, particularly those with PD-L1–positive tumors.