We identified 1549 patients with dMMR/MSI-H CRC; 242 patients of these had received pembrolizumab or nivolumab….High expression of HLA genes (HLA-DRB1, HLA-B, HLA-DQB1, HLA-DPB1, HLA-DPA1- p<0.02; fold change 2.1-3) was found in the good responder group...patients in the highest quartile of expression for either CD74, HLA-DQA1, HLA-DQB1, HLA-DPB1 or HLA-DRB1 had improved survival when compared to lower expressors (p< 0.05).