L'immunohistochimie PD-L1 dans les cancers pulmonaires non à petites cellules, perspectives d'avenir

PD-L1 detection by immunohistochemistry (IHC) is the only predictive biomarker available to date for PD-L1/PD1 immunotherapy in thoracic oncology. While many studies have been published in the domain of this biomarker, they raise a number of questions mainly concerning the type of antibody for use and its condition of utilization, the threshold to be used; the message and information to communicate to the thoracic oncologist and; the adoption of this methodology as part of the daily practice of a pathology laboratory. IHC for PD-L1 can be considered as a theranostic test, which implies providing an extremely reliable result that, taken the therapeutic consequences, avoids any false positive and negative results. PD-L1 IHC can be a companion or complementary diagnostic test depending on the clone employed, the molecular therapy prescribed and the indication of use. In this context, assessment of PD-L1 IHC requires considerable expertise and specific training of pathologists, the role of which is crucial in orienting towards the best therapy. International and national recommendations have to rapidly give a better visibility for effective use of different anti-PD-L1 antibodies.This review provides an update on the use of the different PD-L1 antibodies for IHC in the context of metastatic non-small cell lung cancer (NSCLC) and discusses their use as companion or complementary diagnostic tests.The limits of PD-L1 IHC as a predictive test, the precautions to be adopted to set up a quality test as well as some perspectives will then be considered.