Post-axitinib systemic therapy in metastatic renal cell carcinoma (mRCC).

4609 Background: Axitinib is a potent and selective inhibitor of the VEGF receptor family with efficacy as a second-line therapy in mRCC. Evaluation of further systemic therapy following axitinib has not been previously reported. Methods: The medical records ofmRCCpatients (pts) treated at The Cleveland Clinic or MD Anderson Cancer Center who received axitinib were retrospectively reviewed. Patient characteristics including best response and duration of treatment on axitinib and each subsequent line of therapy were recorded. Results: Eighty-one patients were initially identified; 29 patients received at least one approved targeted agent following axitinib and are included in this analysis. The remainder of pts were excluded due to ongoing axitinib (n=16), lack of subsequent therapy (n=13), lost to follow up (n=11), received experimental agents post-axitinib (n=7) or were inevaluable (n=2). Three pts were excluded due to ≤ 21 days on axitinib. Pt characteristics at start of axitinib included 76% male, median age 59 (range, 44-78); 97% clear cell; 93% prior nephrectomy; 64% previously-treated. Pts were favorable (39%) or intermediate (60%) risk based on Heng criteria. Overall response rate to axitinib was 52% and median duration of treatment of 11.2 months (range, 1.1-90). Thirty eight percent of patients had new brain, bone, and/or liver metastases at disease progression on axitinib. For the first subsequent therapy post axitinib (n=25), pts were treated with tyrosine kinase inhibitors (72%) or mTOR inhibitors (28%). Overall 8% of pts achieved partial responses (one pt each to sunitinib and pazopanib) and 52% had a best response of stable disease. Estimated median duration of therapy was 4.4 months (range, 0.2-27.5+). Fifteen pts received a second post-axitinib targeted therapy with mTOR inhibitors (60%) or TKIs (40%). One patient (7%) achieved a partial response to pazopanib and 8 patients (53%) had a best response of SD. Estimated median treatment duration was 4.8 months (range, 0.7-19.1+). Conclusions: There are objective responses and stable disease to post-axitinib targeted therapies, consistent with previous series and trials in refractory RCC patients.