Would you consider pembrolizumab for a patient with microsatellite stable stage IV colon cancer with high TMB on liquid biopsy who has progressed on all standard therapies?

The Keynote 158 study demonstrated an objective response rate of 29% in patients with MSS tumors and TMB >=10 mut/MB (Marabelle et al., PMID 32919526). FDA subsequently approved pembrolizumab treatment for patients unresectable or metastatic tumor mutational burden–high (TMB-H; ≥ 10 mutations/megabase [mut/Mb]) solid tumors. Of note, this study used FoundationOne CDx test and the definition of TMB-H varies based on the testing platform so when we are seeing patients, we need to be aware of the potential difference of TMB from different test. So it will be reasonable to consider immunotherapy for this patient mentioned in the question (patient with microsatellite stable stage IV colon cancer with high TMB on liquid biopsy who has progressed ...