PDCD1 and lung cancer: The first breakthrough in the utility of ICIs in treatment of lung cancer was in the form of PD-1 inhibitor nivolumab as second-line therapy for patients with advanced NSCLC, when randomized phase III trials showed superior objective response rate (ORR) and OS with nivolumab compared to docetaxel in patients with advanced squamous and non-squamous NSCLC following progression on platinum-based chemotherapy (6, 7).