In the absence of disease progression, durvalumab was an approved treatment option after concomitant chemoradiotherapy. The KEYLYNK-012 study was a multicenter, phase III, randomized, placebo- and active-controlled, double-blind trial to determine if starting immunotherapy with pembrolizumab concurrently with chemoradiotherapy, followed by post-chemoradiotherapy pembrolizumab with or without olaparib improves outcomes for people with stage III NSCLC. Participants must be more than or equal to 18 years old and have previously untreated, pathologically proven, stage IIIA-C, squamous, or nonsquamous NSCLC that is not appropriate for curative surgery. For 3 cycles, participants were randomized 1:1:1 to platinum-doublet chemotherapy plus pembrolizumab radiation (Groups A and B) or concurrent chemoradiotherapy alone (Group C). In addition, participants received pembrolizumab plus olaparib placebo (Group A), pembrolizumab plus olaparib (Group B), or durvalumab monotherapy if disease progression was not detected (Group C). Progression-free survival measured by RECIST version 1.1 by an independent central review and overall survival were the 2 key objectives. Enrollment started on July 6, 2020, and was still going on at over 190 locations. In patients with unresectable stage III NSCLC, KEYLYNK-012 offered critical information on the efficacy and safety of pembrolizumab plus concurrent chemoradiotherapy, followed by pembrolizumab with or without olaparib.