435 Background: Given a lack of clinical information on therapeutic efficacy of agents following progression after vascular endothelial growth factor (VEGF) tyrosine kinase inhibition (TKI) and mammalian target of rapamycin (mTOR) inhibition in metastatic renal cell carcinoma (mRCC), we investigated the activity of single agent bevacizumab (B) in this setting. METHODS We conducted a retrospective analysis of single agent B-treated patients with mRCC in the second/third line setting, and identified 21 subjects who met inclusion criteria. The primary endpoint was progression-free survival (PFS). Baseline characteristics, survival, response efficacy outcomes, and toxicities were assessed and summarized. RESULTS 21 patients (15 women/6 men) were treated with B at a dose of 5 mg/kg/week, dosed q2-3 weeks. Median age was 63, 80% were white, 14% black; 80% had clear cell histology. Median time from diagnosis to B therapy was 3 years (range 1-18); 100% had prior VEGF TKI therapy; 43% had prior mTOR inhibitor; 43% had prior IFN and 19% prior IL-2; median number of prior therapies was 3 (range 1-7); 100% were considered Motzer intermediate risk. Median PFS on B for all subjects was 4.4 mo (95% CI 2.8-9.6) and median OS was 19.4 mo (95% CI 9.9-NR) from start of B therapy. ORR was 2 CR/PR (9.5%), 11 SD (52%), 5 PD, 3 NE. For subjects treated with prior VEGF and mTOR inhibitors, median PFS and OS were 4.4/13.2 mo. Toxicities were as expected and severe adverse events included grade 3-4 fatigue (6), grade 3-4 dehydration (5), and grade 4 failure to thrive (2), grade 4 constipation (2), and grade 3 muscle weakness (2). CONCLUSIONS Single agent B therapy has acceptable toxicity and moderate disease stabilizing activity in selected patients with mRCC who have failed prior VEGF TKI and mTOR inhibitor therapy, and suggests a benefit to continued ongoing VEGF inhibition. Further prospective study of B alone, in combination with mTOR inhibition, or with alternative targeted agents is warranted.