A Phase 3, Randomized, Double-blind, Placebo- and Active-Comparator-Controlled Study of MK-1084 Plus Durvalumab Versus Placebo Plus Durvalumab in Participants With Locally Advanced, Unresected KRAS G12C-Mutant Non-Small Cell Lung Cancer Without Disease Progression Following Definitive Platinum-Based Chemoradiotherapy (KANDLELIT-015)

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: * Has a histological or cytological diagnosis of locally advanced, unresected Stage II (node-positive) to III non-small cell lung cancer (NSCLC) with predominantly nonsquamous histology. * Has completed definitive platinum-based concurrent chemoradiotherapy (CCRT) prior to enrollment, without disease progression. * Has provided a tumor tissue sample for central laboratory testing of Kirsten rat sarcoma G12C (KRAS G12C) status, programmed cell death ligand 1 (PD-L1) status, and biomarker research. * Tumor tissue sample has a demonstrated presence of KRAS G12C mutation and an evaluable PD-L1 status result. * If human immunodeficiency virus (HIV)-infected, has well-controlled HIV on antiretroviral therapy (ART). * If hepatitis B surface antigen (HBsAg)-positive, has undetectable hepatitis B virus (HBV) viral load and has received HBV antiviral therapy. * If has a history of hepatitis C virus (HCV) infection, has undetectable HCV viral load. * Has a body weight ≥35 kg. Exclusion Criteria: The main exclusion criteria include but are not limited to the following: * Has a diagnosis of small cell lung cancer or mixed tumors with small cell elements. * Has a gastrointestinal disorder affecting absorption or is unable to swallow orally administered medication. * Has active inflammatory bowel disease requiring immunosuppressive medication or previous clear history of inflammatory bowel disease. * Has uncontrolled, significant cardiovascular disease or cerebrovascular disease. * Is HIV-infected with a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease. * Has received prior treatment (other than definitive CCRT) for NSCLC. * Has a known additional malignancy that is progressing or has required active treatment within the past 3 years. * Has an active autoimmune disease that has required systemic treatment in the past 2 years. * Has a history of, or has current, (noninfectious) pneumonitis/interstitial lung disease that required/requires steroids. * Has an active infection requiring systemic therapy. * Has a history of stem cell/solid organ transplant. * Has not adequately recovered from major surgery or has ongoing surgical complications.