Studies have shown that immune CPI monotherapy, including PD-1 blockade or anti-CTLA-4 therapy, is associated with virtually no activity in patients with pMMR/non-MSI-H metastatic CRC (Asaoka et al., 2015; Le et al., 2017), while approximately 10–15% of CRC tumors are associated with MSI (Boland and Goel, 2010). This evidence concerns the gene PDCD1 and colorectal carcinoma.