Investigation of Regorafenib Efficacy in Patients with Metastatic Colorectal Carcinoma in Relation to the Delivered Dose Intensity/Body Surface Area

The significance of relative dose intensity (RDI) in the treatment of various types of solid cancers has been studied. Nevertheless, RDI may not accurately reflect the treatment intensity of regorafenib, where the standard dose cannot be tolerated by most patients. We aimed to investigate the efficacy of the delivered dose intensity/body surface area (BSA) ratio at 2 months (2M-DBR) by comparing the relationship between 2M-DBR, RDI at 2 months, and the therapeutic response. Material and Methods: The thera- peutic response to regorafenib was studied in 53 patients retrospectively from 2015 to 2020. Computed tomography scans were performed at 8-12 weeks after the initiation of treatment. We also investigated the clinical factors associated with high 2M-DBR and BSA. Results: Pa- tients with high 2M-DBR achieved significantly better objective response rates than those with low 2M-DBR (p<0.064). Patients with high 2M-DBR experienced longer overall survival (p=0.445) and progression-free survival (p=0.524) than those with low 2M-DBR but the dif- ference was not statistically significant. Tolerance to 160 mg regorafenib was found to be better in patients with high BSA (22%) than in a patient with low BSA (0%) (p=0.011). Conclusion: BSA is crucial in determining the tolerance dose of regorafenib. 2M-DBR plays a key role in reflecting treatment intensity and is a useful tool for predicting the response to regorafenib in mCRC.