Comparison of Standard Initial Dose and Reduced Initial Dose Regorafenib for Colorectal Cancer Patients: A Retrospective Cohort Study.

<bold>Background: </bold>The benefit of regorafenib for colorectal cancer patients was demonstrated in previous randomized studies. However, these studies showed a high rate of treatment-related adverse events, and adverse events were more common in Japanese patients. Some studies showed fewer adverse events and a longer survival time with a reduced initial dose. However, the benefits of a reduced initial dose of regorafenib have only been evaluated in small samples.<bold>Objective: </bold>Our objective was to analyze the efficacy of initial regorafenib dose reduction compared with a standard dose for colorectal cancer patients.<bold>Patients and Methods: </bold>We used a hospital-based nationwide claims database. Patients who received regorafenib for metastatic colorectal cancer between June 2013 and July 2017 were included in this study. We divided the patients into a standard initial dose group (standard group) and a reduced initial dose group (reduced group). Overall survival (OS) and adverse events were compared between the two groups. We performed propensity score matching for sensitivity analysis.<bold>Results: </bold>We included 2376 patients (1208 in the standard group and 1168 in the reduced group). The median OS was 12.3 months (95% confidence interval (CI): 11.0-13.3) in the standard group and 12.6 months (95% CI: 11.7-13.6) in the reduced group. A log-rank test showed no significant difference between the two groups (p = 0.41). Most adverse events occurred less frequently in the reduced group. In the sensitivity analysis, there was no significant difference for OS.<bold>Conclusions: </bold>No significant difference was observed for OS between the standard group and the reduced group. However, there were fewer adverse events in the reduced group. The optimal initial dose of regorafenib should be identified in further studies. [ABSTRACT FROM AUTHOR]