Sunitinib administered on 2/1 schedule in patients with metastatic renal cell carcinoma: the RAINBOW analysis

Background: First-line sunitinib is recommended in metastatic renal cell carcinoma (mRCC), but it is frequently associated with relevant toxicities and subsequent dose reductions. Alternative schedules, such as 2-week-on treatment and 1-week-off (2/1 schedule), might improve tolerability. We evaluated the safety and outcomes of this schedule in a large multicenter analysis. Patients and methods: Retrospective, multicenter analysis of mRCC patients treated with first-line sunitinib on a 2/1 schedule. Data of 249 patients were reviewed: 208 cases who started sunitinib on the 4/2 schedule (full dosage: 188/208, 90.4%) and thereafter switched to the 2/1 schedule for toxicity (group 4/2. 2/1) and 41 patients who started first-line sunitinib with the 2/1 schedule because of suboptimal clinical conditions (group 2/1). A total of 211 consecutive patients treated with the 4/2 schedule in another institution served as external controls. Safety was the primary end point. Treatment duration (TD), progression-free survival (PFS) and overall survival (OS) were also analyzed. Results: In group 4/2 -> 2/1, the overall incidence of grade >= 3 toxicities was significantly reduced (from 45.7% to 8.2%, P < 0.001) after the switch to 2/1 schedule. This advantage was maintained also in the 106/188 cases (56.4%) who maintained the full dosage. Fatigue, hypertension, hand-foot syndrome and thrombocytopenia were less frequent. The incidence of grade >= 3 adverse events in the negatively selected group 2/1 (only 73.2% starting at full dose) was 26.8%, similar to what observed in the external control group (29.4%). Median TD was 28.2 months in the 4/2 -> 2/1 group (total time spent with both schedules), 7.8 months in the 2/1 group and 9.7 months in external controls. Median PFS was 30.2, 10.4 and 9.7 months, respectively. Median OS was not reached, 23.2 and 27.8 months, respectively. Conclusions: mRCC patients who moved to a modified 2/1 schedule of sunitinib experience an improved safety profile compared with that observed during the initial 4/2 schedule.