Regorafenib and Nivolumab or Pembrolizumab Combination and Circulating Tumor DNA Response Assessment in Refractory Microsatellite Stable Colorectal Cancer

Background Metastatic colorectal cancers (MCRCs) with microsatellite stability (MSS) are resistant to immunotherapy with programmed cell death protein 1 (PD-1) and programmed death-ligand 1 inhibitors. However, the addition of regorafenib to nivolumab was recently associated with a high response rate and a protracted progression-free survival in a small cohort of MSS Japanese patients with metastatic colorectal cancer. Materials and Methods We...