Use of Immune Checkpoint Inhibitors in Mesothelioma.

Recent advances in immunology have extended into the mesothelioma field. To date, only Japan has given regulatory approval to salvage nivolumab in chemo-refractory mesothelioma patients. The USA has included in the NCCN guidelines that pembrolizumab (in programmed death ligand 1 (PD-L1) immunohistochemistry (IHC)-positive patients) and nivolumab with or without ipilimumab (whatever the PD-L1 status is) are accepted salvage therapies. Based on the growing body of literature, it is anticipated that checkpoint inhibitors will receive regulatory approval in the USA and Europe soon for salvage therapy. Additional research efforts will determine whether earlier stage patients and frontline unresectable patients will benefit from the addition of immunotherapy to their treatment regimens. The realm of biomarker research has lagged behind in mesothelioma. In general, mesothelioma has less tumor mutation burden than other malignancies. Most of the single-agent salvage checkpoint inhibitor trials have shown a trend correlating higher PD-L1 immunohistochemistry (IHC) with responses. However, survival data remains immature and a larger number of patient outcomes are needed to ascertain the value of PD-L1 IHC as a predictive biomarker. Incorporation of translational studies in all immunotherapy trials and especially window-of-opportunity resectable studies should be supported and instituted in all future mesothelioma trials.