Evaluation of response from axitinib per Response Evaluation Criteria in Solid Tumors versus Choi criteria in previously treated patients with metastatic renal cell carcinoma

BACKGROUND: Axitinib, a selective and potent tyrosine kinase inhibitor of vascular endothelial growth factor receptors, was available to patients from Canada and Australia, prior to regulatory approval of axitinib in these countries, for treatment of clear-cell metastatic renal cell carcinoma (mRCC) after failure of one prior systemic regimen. METHODS: This single-arm, open-label study of axitinib evaluated the efficacy, safety, and quality of life (QoL) in patients with mRCC whose disease progressed after one prior systemic first-line regimen. Primary objective was objective response rate evaluated per Response Evaluation Criteria in Solid Tumors (RECIST) and Choi criteria. Progression-free survival, overall survival, safety, and QoL were secondary end points. Due to the small study size, analyses comprised of descriptive statistics. RESULTS: Fifteen patients were recruited, five from Canada and ten from Australia, over a limited recruitment period. Thirteen patients received sunitinib as prior therapy. All patients had clear-cell carcinoma, eleven had prior nephrectomy. Liver, lung, and lymph nodes were the most frequent sites of metastases; one patient had brain metastasis. Median time on axitinib was 118.0 days (range: 3.5–645.0 days); estimated survival probability at 12 months was 57.8%. Two (13.3%) patients had objective responses per RECIST versus nine (60.0%) per Choi criteria. Six patients had progressive disease based on RECIST versus three per Choi criteria. Nine (60.0%) events of progression or death occurred by the end of study, and three patients continued to receive the study drug. Fatigue (33%) and diarrhea (20%) were the most common grade ≥3 all-causality, treatment-emergent adverse events. The mean change in European Quality of Life – 5 Dimensions score from baseline to end of treatment was −0.0837. CONCLUSION: The small number of patients and lack of a comparator arm limit the ability to draw definitive conclusions; however, safety and efficacy profiles of axitinib were consistent with reports from previous studies in patients with mRCC, and patients generally maintained QoL. The sizeable difference observed in objective response rate by RECIST versus Choi criteria merits further research.