To evaluate the efficacy and safety of Pembrolizumab + Pemetrexed in elderly patients with non-squamous non-small cell lung cancer with Programmed cell death (PD) -ligand1 (L1) tumor proportion score (TPS) of less than 50%.Primary endpoint is overall response rate and secondary endpoints are progression free survival (PFS), 1 year PFS rate, overall survival and adverse event.

