The combination of atezolizumab plus bevacizumab may offer some benefit to patients with advanced renal cell carcinoma, especially those who are positive for programmed death-ligand 1 (PD-L1), investigators report.
The overall response rate (ORR) among such patients was 60%, compared with 19% in PD-L1–negative patients, Bradley A. McGregor, MD, clinical director for the Lank Center of Genitourinary Oncology at Dana-Farber Cancer Institute in Boston, and colleagues reported in the Journal of Clinical Oncology.
The data were presented last summer at the American Society of Clinical Oncology Annual Meeting in Chicago.
The phase 2 study comprised 60 patients, 42 of whom had variant histology RCC, and 18 of whom had clear cell RCC (ccRCC ) with at least 20% sarcomatoid differentiation. All patients had advanced renal cell carcinoma of various histologies, including papillary (12), chromophobe (10), unclassified (9), TFE3 translocation (5), collecting duct (5), and medullary (1). Most (65%) had not received prior systemic therapy.
They all received infusions of atezolizumab 1,200 mg plus bevacizumab 15 mg/kg every 3 weeks. No dose modifications were allowed. Dose delays were allowed, and patients could also drop one agent and continue with the other. Treatment continued until disease progression, toxicity, or intolerable side effects.
The median number of cycles was 9.5, although the range was wide (1-42). At analysis, 15 were still on the treatment, but 45 had dropped out. Reasons were disease progression (34), death (1), toxicity (5), or unspecified (8). Six patients delayed bevacizumab doses, half because of adverse events.
After a median follow-up of 13 months, the ORR was 33%. Those with ccRCC with sarcomatoid differentiation responded best to the combination (ORR, 50%). Those with variant-histology RCC responded less robustly (ORR, 26%).
ORR varied by baseline risk category, being 33% in favorable-, 45% in intermediate-, and 11% in poor-risk patients. Median time to response was 2.7 months, median response duration was 8.9 months, and median progression-free survival was 8.3 months.
PD-L1 status was determined in 36 patients; 15 were positive. Among the positive patents, ORR was 60%, compared with 19% in PD-L1 negative patients. Response rates varied with tumor characteristics. Among patients with ccRCC with sarcomatoid differentiation, the ORR was 50% in PD-L1–positive patients and 29% in negative patients. In patients with variant histology RCC, the ORR was also better in PD-L1 positive patients (67% vs. 14%).
The most common treatment-related side effects were fatigue (35%), proteinuria (35%), musculoskeletal pain (33%), diarrhea (22%), rash (20%), hypertension (18%), pruritus (18%), thyroid dysfunction (17%), hepatitis (15%), fever (13%), and mucositis (12%). Thirty-four patients developed at least one grade 3 adverse event; there were no grade 4 or 5 toxicities. One patient died, presumably because of disease progression.
Quality of life scores were largely stable during treatment.
“The combination demonstrated responses across several subtypes of RCC, including collecting duct and medullary carcinoma, histologies that are often treated with cytotoxic chemotherapy,” the authors said. “This is notable given the generally poor prognosis and low response rate associated with variant histology RCC in trials to date.”
The study also suggests the PD-L1 status might be “intriguing as a biomarker for response to atezolizumab and bevacizumab in variant histology RCC. We plan to conduct additional correlative work, including genomic profiling and assessment of the immune microenvironment, to better elucidate markers of response and resistance,” the authors wrote.
SOURCE: McGregor BA et al. J Clin Oncol. 2019 Nov 13. doi: 10.1200/JCO.19.01882.