PDCD1 and colorectal carcinoma: Approximately 25% of MSI-H CRC patients display intrinsic resistance to immunotherapy, with objective remission rates (ORR) of 38% for anti-PD-1 monotherapy and 54% for anti-PD-L1 monotherapy, while anti-PD-1 combined with anti-CTLA-4 therapy achieves the highest ORR of 57% [142].