Study of Durvalumab+Olaparib or Durvalumab After Treatment With Durvalumab and Chemotherapy in Patients With Lung Cancer (ORION)

Inclusion Criteria: \- Histologically or cytologically documented Stage IV NSCLC not amenable to curative surgery or radiation. Patients must have tumors that lack activating EGFR mutations and ALK fusions. * (WHO)/(ECOG) performance status of 0 or 1 * No prior chemotherapy or any other systemic therapy for Stage IV NSCLC * Adequate organ and marrow function without blood transfusions in the past 28 days, * At least 1 tumor lesion, not previously irradiated, that can be accurately measured as per RECIST 1.1. Key Inclusion criteria for randomization to maintenance treatment: * Documented radiographic evidence of CR, PR, or Stable Disease (SD) as per Investigator-assessed RECIST 1.1 following 4 cycles of platinum-based chemotherapy. * Creatinine Clearance (CrCl) ≥51 mL/min calculated by the investigator or designee using the Cockcroft-Gault equation or measured by 24-hour urine collection. * Ability to swallow whole oral medications. * All patients must provide a formalin-fixed, paraffin embedded tumor sample for tissue-based immunohistochemistry staining and DNA sequencing to determine PD-L1 expression, HRRm status, and other correlatives: either newly acquired or archival tumor samples (\<3 years old) are acceptable. If available, a newly acquired tumor biopsy, collected as part of routine clinical practice, is preferred. If not available, an archival sample taken \<3 years prior to screening is acceptable. If both an archival sample and a fresh tumor biopsy sample are a…