Microsatellite instable tumors often respond to immune checkpoint blockade (ICB), however, tumor tissue is unavailable/insufficient in some patients. Two groups are reporting a blood-based assessment of the microsatellite status validated in tumor tissue and by clinical benefit in patient receiving ICB. Both approaches are highly appealing with a few caveats.See related articles by Georgiadis et al., p. 7024, and Willis et al., p. 7035.
©2019 American Association for Cancer Research.