Aim: To determine a recommended Phase II dose of the oral fluoropyrimidine trifluridine/tipiracil (FTD/TPI) combined with the multi-kinase inhibitor regorafenib (REG) in refractory metastatic colorectal cancer patients. Materials & methods: A conventional 3 + 3 dose finding design was used. FTD/TPI was administered on days 1-5 and 8-12 of a 28-day cycle, REG on days 2-22. Two dose levels were used: FTD/TPI 25 mg/m2 b.i.d. + REG 120 mg/d, then escalated to FTD/TPI 35 mg/m2 b.i.d. + REG 120 mg/d. Results: In total, 12 patients were treated at two dose levels. Three dose-limiting toxicities were observed; all were grade 3 hypertension causally attributed to REG. Recommended Phase II dose is FTD/TPI 25 mg/m2 b.i.d. + REG 120 mg/d. Median progression-free survival was 3.81 months (95% CI: 1.51-5.29), median OS 11.1 months (95% CI: 2.3-18.2). Conclusion: The combination of REG and FTD/TPI is feasible and safe. Efficacy signals exceed that of the single agents at acceptable toxicity levels and are clinically meaningful.
