Dissecting Response and Resistance to Anti-PD-1 Therapy in Microsatellite-Unstable Gastric Cancer.

Most, but not all, patients with microsatellite-unstable gastric cancer respond to anti-PD-1 therapy. In this issue, Kwon and colleagues show, first, that differences in tumor mutation burden (TMB) may drive this variation in outcomes and, second, that treatment with immune checkpoint inhibitors leads to further immunoediting and a reduction in TMB in responding patients.See related article by Kwon et al., p. 2168.