Background: SUN is approved in mRCC setting at the dose of 50mg daily for 4 weeks followed by 2 weeks rest (4/2 schedule). The 4/2 schedule often requires dose modifications for toxicity. Current recommendation is to reduce the dose to 37.5mg per day. Alternative schedules (2 weeks of treatment followed by one-week rest (2/1 schedule) have shown promising results. SURF trial evaluated prospectively schedule 2/1 when toxicity occurs. Methods: SURF [NCT02689167] is a prospective, non-comparative randomized study. Patients (pts) with mRCC (clear cell) were included at SUN initiation. When a dose adjustment of SUN was required, patients were randomized between 4/2 schedule at 37.5mg daily and experimental 2/1 schedule at 50mg daily. Primary objective was to assess duration of SUN treatment among the 73 first evaluable pts. Overall 226 pts were enrolled with 133 randomized. All other analyses are shown for the 133 randomized patients. Results: Pts were 75.2% males, with a median age 63.7 years for 94% with a Karnofsky ≥ 80%. Of them, 54.9% had partial/total nephrectomy. IMDC risk score was favourable (45.1%), intermediate (46.6%) or poor (8.3%). Pts characteristics were well balanced between 2 arms. Metastatic sites were lungs (60.5%), bones (16.3%), lymph nodes (15.5%). At 6 months, 48 patients (65.8%) of the 2/1 schedule were still on treatment (above predefined threshold for positivity). Other data are listed on the table. No new safety signal was identified. Permanent SUN discontinuation due to toxicity was 22.2% in control arm vs 12.3% in experimental arm. Conclusions: SURF is the largest prospective randomised trial evaluating two different SUN schedules modifications in mRCC in case of toxicity. This positive trial confirms the role of adapting SUN to a 2/1 schedule rather than reducing SUN dose to the classical 4/2 schedule. Clinical trial information: NCT02689167.