Clinical trials have proven the power of immunotherapies targeting PD-L1 or PD-1 in a range of cancers. However, these same trials show that only some patients benefit – tumors must depend on PD-L1 to be affected when medicines block its action. In response, the companies Merck, AstraZeneca, Genentech/Roche, and Bristol-Myers Squibb together with the diagnostic companies Ventana and Dako have developed four tests to predict which tumors do and do not express on PD-L1 and thus which tumors will respond to the therapies. An ambitious collaboration between these companies and research organizations including the International Association for the Study of Lung Cancer, the American Association for Cancer Research, and academic medical centers including the University of Colorado Cancer Center, results in a study published online today in the Journal of Thoracic Oncology comparing these four tests.
The study, called the “Blueprint PD-L1 IHC Assay Comparison Project,” used all four tests to evaluate 38 samples of human non-small cell lung cancer. In all four tests, half of the tumors were positive for PD-L1 and 5 of the tumors were negative. However, in 14 of 38 cases (37 percent), some tests considered the sample positive while others considered it negative. The disagreement implies that the choice of test used to determine a tumor’s PD-L1 dependence may influence whether or not a patient is offered anti-PD-L1 therapy.