Treatment patterns, efficacy and toxicity of regorafenib in gastrointestinal stromal tumour patients.

Regorafenib was approved as third-line therapy for advanced Gastrointestinal Stromal Tumour (GIST) at a starting dose of 160 mg daily 3 weeks on, 1 week off, based on improvement in progression free survival over placebo (4.8 vs. 0.9 months), but the response rate was low at 4.5%. Given the high toxicity rate in GIST patients, there is variability in the post-marketing dosing of regorafenib. We aimed to summarize our experience regarding prescribing patterns, efficacy and toxicity of regorafenib and determine the role of response assessment by Choi criteria in GIST patients. We included 28 patients who received regorafenib from our pharmacy. Baseline patient characteristics and treatment outcomes were recorded and an independent radiologist assessed response using Choi and RECIST. Seventy-nine percent of patients started at a 120 mg continuous daily dosing schedule, different from the standard intermittent dosing schedule. Grade 3/4 adverse events were experienced by 43% of patients. Median progression-free survival was 8.7 months. Continuous dosing with regorafenib at 120 mg daily is the preferred prescribing pattern and appears to be better tolerated and with comparable efficacy to the current standard dose. Similar to imatinib, the partial response rate for regorafenib by Choi (29%) was higher compared to RECIST (4%).