Regorafenib combined with immune checkpoint inhibitors versus regorafenib monotherapy as a late-line treatment for metastatic colorectal cancer: a single-center, retrospective cohort study

Background: Few data are available on metastatic colorectal cancer (mCRC) treated with late-line regorafenib monotherapy or combined with other therapies. This study thus aimed to examine regorafenib combined with immune checkpoint inhibitors (ICIs) compared with regorafenib monotherapy in patients with advanced CRC. Methods: This single-center retrospective cohort study included patients with advanced CRC who experienced recurrence and progression after standard first- and second-line treatments treatment from November 2018 to December 2021. The patients received regorafenib plus ICIs or regorafenib monotherapy. Treatment response was evaluated based on Response Evaluation Criteria in Solid Tumors (RECIST). Overall survival (OS) and progression-free survival (PFS) were analyzed via multivariate analysis. Results: The combined group and the monotherapy group included 30 and 43 patients, respectively. The median OS (13.7 vs. 10.1 months; P=0.10) and PFS (4 vs. 3.6 months; P=0.32) were not significantly different between the two groups. In males, the median OS was significantly longer in the combined group compared with the monotherapy group (not reached vs. 8.03 months; P=0.02), but the median PFS showed no significant difference (7.23 vs. 3.90 months; P=0.16). There was no significant difference in OS (P=0.71) or PFS (P=0.89) in females. Eastern Cooperative Oncology Group performance status (ECOG PS) 1 [vs. 0; hazard ratio (HR) =3.13, 95% confidence interval (CI): 1.61-6.10; P<0.001] was independently associated with PFS. ECOG PS 1 (vs. 0; HR =3.63, 95% CI: 1.54-8.56; P=0.003) and combined therapy (vs. monotherapy; HR =0.47, 95% CI: 0.22-0.99; P=0.048) were associated with OS. Conclusions: Regorafenib combined with ICIs led to numerically longer PFS and significantly prolonged OS in patients with mCRC compared to regorafenib monotherapy, especially in male patients.