Overcoming sunitinib-induced resistance by dose escalation in renal cell carcinoma: Evidence in animal models and patients.

4582 Background: Sunitinib is considered a first-line therapeutic option for patients with advanced clear cell renal cell carcinoma (ccRCC). However, despite the clinical efficacy, eventually tumors develop resistance and progress. Thus, we have tested the hypothesis whether sunitinib dose-escalation could overcome initial drug resistance. Methods: Human patient-derived ccRCC xenografts were implanted in SCID mice and were randomly assigned into two groups (sunitinib and vehicle). Mice were treated with sunitinib 5 days/week with a dose-escalation schema starting from 40 mg/kg to 60 mg/kg and 80 mg/kg. Tumor volumes and body weights were assessed weekly. Tumor tissues and blood were collected prior to dose increments. In selected patients treated with 50 mg sunitinib and presenting minimal toxicities, dose was escalated to 62.5 and 75 mg at the time of tumor progression. Results: Our preclinical results show that patient-derived tumors (RP-01 and RP-02), although initially responsive to sunitinib 40 mg/kg...