Association Of Pd-L1 Mrna Levels In Plasma-Derived Exosomes With Response To Nivolumab And Pembrolizumab In Melanoma And Nsclc.

210Background: The anti-PD-1 monoclonal antibodies (moAb) nivolumab and pembrolizumab have improved the survival of melanoma and non-small cell lung cancer (NSCLC) patients. However, treatment selection is based on tumor PD-L1 expression by immuno-histochemistry and no specific approaches are available to monitor treatment response. The aim of this study was to investigate the association between PD-L1 mRNA levels in plasma-derived exosomes and response to nivolumab and pembrolizumab in patients affected by melanoma (n = 18) and NSCLC (n = 8). Methods: Blood (6 ml) was obtained at 1) baseline (before initiation of anti-PD1 moAb or at the time of last available radiological evaluation of disease response) and 2) after two months of treatment (at the time of first response evaluation or disease re-assessment). Exosomes were extracted from plasma and PD-L1 mRNA expression was measured by digital PCR and expressed as copies/ml. Results: Overall, the number of copies of mRNA PD-L1/ml plasma varied according to...