[Predictive markers of immunotherapy of cancer, practical issues of PD-L1 testing].

Pathologists have detected signs of antitumor immune reactions for a long time but only in case of a few cancer types became this part of the report. The advent of immunotherapy of cancers, however, radically alters this routine and promotes the development of clinically valid prognostic and predictive immunological makers. The most advanced immunological markers are the Immunoscore (density of T-cell subpopulations), and PD-L1 protein expression on tumor or immune cells. PD-L1 testing of cancers raises new issues since almost all novel therapies developed its own in vitro diagnostics. Due to the incompatibility of these assays it is suggested to use the companion diagnostic of the given immunotherapeutic drug defined in its label.