BACKGROUND: The most effective treatment of immune checkpoint inhibitors (ICIs) 
is restricted in microsatellite instability (MSI-H) subsets of advanced 
colorectal cancer, but MSI-H only accounts for 4-5% among them. ICIs are 
completely ineffective in advanced colorectal cancer patients with 
microsatellite stable (MSS), according to literatures published. Regorafenib is 
a novel tyrosine kinase inhibitor (TKIs) that could normalize tumor blood 
vessels by inhibiting vascular endothelial growth factor receptor and its 
downstream, thus improving cytotoxic T cell infiltration in tumor 
microenvironment, which has a synergistic effect with ICIs. Toripalimab is a 
type of anti-PD-1 monoclonal antibody produced by Junshi Biosciences in China. 
Herein, we aimed to explore the efficacy and safety of regorafenib combined with 
toripalimab in the third-line and beyond treatment of advanced colorectal 
cancer.
METHODS: We evaluated the outcomes of MSS patients with advanced colorectal 
cancer who received regorafenib combined with toripalimab in the Second 
Affiliated Hospital of Nanchang University from June 2019 to January 2021. These 
patients had previously received at least second-line treatment; the regimens 
were oxaliplatin and irinotecan-based chemotherapy and/or accompanied with 
bevacizumab or cetuximab. Thirty-three patients were treated orally with 
regorafenib 80 mg or 120 mg once daily for 21 days, 28 days as a cycle, combined 
with intravenous toripalimab until disease progression or intolerant to adverse 
reactions. We used the Kaplan-Meier method to estimate the rate of 
progression-free survival (PFS) and log-rank method to do a statistical test of 
the survival curve. The Cox regression model was used to analyze the influence 
of multiple factors on PFS. The primary endpoints were objective remission rate 
(ORR) and disease control rate (DCR). The secondary endpoints were the incidence 
of adverse reactions and median progression-free survival (mPFS).
RESULTS: The evaluation of treatment effects was assessed according to RECIST 
1.1. Four patients (12.12%) got partial response, twelve patients (36.36%) 
experienced stable disease, and seventeen patients (51.52%) suffered progressive 
disease. ORR was 12.12% and DCR was 48.48%. mPFS was 113 days (95% CI: 0-272.1). 
In univariate analysis, patients who had previously received second-line 
treatment were significantly better than those who had received third-line or 
more treatment (p=0.005). Lung metastasis was a negative factor in combined 
therapy (p=0.032). Five patients without previous treatment of bevacizumab were 
effective. Previous treatment without bevacizumab showed a trend of effective 
when combination therapy (p=0.034). It was also a positive factor that the 
Eastern Cooperative Oncology Group performance status (ECOG) score was 0 
(p=0.034). Multivariable Cox regression analysis showed the number of previous 
chemotherapy lines and excision of primary lesions were independent prognostic 
factors. The most common treatment-related adverse reactions were hand-foot 
syndrome (33.33%), liver dysfunction (27.27), hypothyroidism (24.24%), fever 
(24.24%), fatigue (21.21%), leukopenia (15.15%), hypertension (12.12%), platelet 
count decreased (6.06%), diarrhea (3.03%), and myocarditis (3.03%); one patient 
stopped treatment as myocarditis. The incidence of grade 3/4 adverse reactions 
was 9.09%.
CONCLUSIONS: Regorafenib combined with toripalimab has a promising effect in the 
third-line and beyond treatment of advanced colorectal cancer. In the early use 
of combination therapy, excision of primary lesions can have a positive impact 
in regorafenib and toripalimab combination. This treatment-related adverse 
reactions are tolerant in combined therapy.