Regorafenib for advanced gastrointestinal stromal tumors following imatinib and sunitinib treatment: a subgroup analysis evaluating Japanese patients in the phase III GRID trial

The randomized, double-blind, placebo-controlled GRID trial tested the oral multikinase inhibitor regorafenib in 199 patients with advanced gastrointestinal stromal tumors (GIST) following failure of at least imatinib and sunitinib, and showed a significant improvement in progression-free survival (PFS) versus placebo [hazard ratio (HR) 0.27; 95 % confidence interval (CI) 0.19-0.39; p < 0.0001]. A subgroup analysis of Japanese patients in the GRID study was performed to compare the efficacy and safety of oral regorafenib 160 mg once daily with matching placebo, in combination with best supportive care. The primary study endpoint was progression-free survival (PFS); safety was evaluated through the incidence of adverse events (AEs). Seventeen Japanese patients were randomized to regorafenib (n = 12) or placebo (n = 5). Patient demographics were consistent with those of the overall study population. PFS was significantly longer with regorafenib than placebo (HR 0.08; 95 % CI 0.02-0.45; p = 0.000164). Centrally assessed disease control rates were 58 % and 20 % in the regorafenib and placebo groups, respectively (p = 0.080796). Treatment-related adverse events (AEs) were reported in all regorafenib-treated patients and 60 % of placebo recipients; the most frequent AE was hand-foot skin reaction (HFSR) (92 % versus 20 %, respectively). Regorafenib showed efficacy and a manageable safety profile in Japanese patients with advanced GIST, consistent with the overall GRID study population. AEs, such as HFSR and maculopapular rash, were observed more frequently in Japanese patients. Although dose modification was frequently reported, only one patient with hepatic failure discontinued regorafenib because of AEs.