In 2017, Foundation Medicine and Flatiron Health created a proof-of-concept study. Using a sample size of over 2000 patients with non–small cell lung cancer, they discovered that high versus low tumor mutation burden showed a far stronger association than high versus low PD-L1 levels after immunotherapy. Their results were nearly identical to those derived by a drug manufacturer from a post hoc analysis of a failed clinical trial. The validation study helped establish the groundwork for this data set to be used to advance cancer research. The gene discussed is CD274; the disease is lung cancer.