Post-cross-over Activity of Regorafenib (RE) in Soft Tissue Sarcoma: Analysis from the REGOSARC Trial.

11052 Background: Based on the placebo (PBO) controlled phase 2 trial (Mir, Lancet Oncol 2016), RE has shown to be an active drug in patients (pts) with leiomyosarcoma (LMS), synovial sarcoma (SS) and other non-adipocytic sarcoma (OTH), but not in liposarcoma. Pts initially allocated to PBO were allowed to cross-over to RE after progression. We here report the activity of RE after cross-over. Methods: From July 2013 to Dec 2014, 138 pts were enrolled in the non-adipocytic sarcoma cohorts (LMS, SS & OTH). After update in Dec 2016, median follow-up was 32 mo (vs 17 mo in the initial publication). Benefit of RE vs PBO in terms of progression-free survival (PFS) and overall survival (OS) from randomization was estimated by hazard ratio (HR) in Cox models. In the PBO arm, intra-patient benefit of RE after cross-over was evaluated by the growth modulation index (GMI), where PFS1=PFS with PBO before cross-over, and PFS2=PFS with RE after cross-over. The impact of timing of RE allocation (delayed after cross-over, vs early at study entry) was evaluated by comparing PFS after cross-over in PBO arm to PFS after randomization in RE arm. Results: As detailed in the table, major PFS benefit of RE vs PBO allocated by randomization was confirmed with long follow-up (HR=0.50 [95%CI 0.35-0.71] p