Evaluation of Factors Predicting the Effectiveness of Regorafenib in the Treatment of Metastatic Colorectal Cancer.

OBJECTIVE: Regorafenib is a multikinase inhibitor, the effectiveness of which was demonstrated in metastatic colorectal cancer. This study aimed to investigate the factors that could predict the effectiveness of regorafenib. MATERIALS AND METHODS: This study retrospectively reviewed the clinical characteristics, tumor characteristics, and previous therapies in 62 patients who presented to our center between 2016 and 2020 and used regorafenib for metastatic colorectal cancer. The effects of the investigated variables on the response obtained with regorafenib use were evaluated. RESULTS: This study included a total of 62 patients diagnosed with metastatic colorectal cancer, of whom 30 (48.4%) were males and 32 (51.6%) were females. Patients' median age at diagnosis was 49 years (18- 68). Regorafenib therapy yielded a disease control rate of 64% [complete response=0, partial response= 14 (28%), and stable disease=18 (36%)]. Objective response was obtained in 28% of patients [complete response=0 and partial response=14 (28%)]. Progression-free survival was 4 months. The evaluation of the effects of patients' age, sex, performance status, previous treatments, metastatic sites, and RAS mutation status on the disease control rate and progression-free survival did not determine any positive or negative effects on progression-free survival. However, left-sided tumors had a positive effect on disease control rate (69.8% vs. 28.6%, P=.029). and previous use of cetuximab had a negative effect on disease control rate [76.5% vs. 37.5% (P=.007)]. CONCLUSION: In our study, tumor localization and previous cetuximab use were found to be correlated with the disease control rate in patients on regorafenib. However, the need for novel biomarkers that will predict the effectiveness of regorafenib in metastatic colorectal cancer treatment persists.