A Study of Atezolizumab Compared With a Single-Agent Chemotherapy in Treatment Naïve Participants With Locally Advanced or Recurrent or Metastatic Non-Small Cell Lung Cancer Who Are Deemed Unsuitable For Platinum-Doublet Chemotherapy

Inclusion Criteria: * Histologically or cytologically confirmed diagnosis of advanced or recurrent (Stage IIIB not amenable for multimodality treatment) or metastatic (Stage IV) NSCLC as per the American Joint Committee on Cancer (AJCC) 7th edition * No sensitizing epidermal growth factor receptor (EGFR) mutation (L858R or exon 19 deletions) or anaplastic lymphoma kinase (ALK) fusion oncogene detected * No prior systemic treatment for advanced or recurrent (Stage IIIB not amenable for multimodality treatment) or metastatic (Stage IV) NSCLC as per the AJCC 7th edition * Life expectancy greater than or equal to (\>/=) 8 weeks * Deemed unsuitable by the investigator for any platinum-doublet chemotherapy due to poor performance status (ECOG performance status of 2-3). However, participants \>= 70 years of age who have an ECOG PS of 0 or 1 may be included due to: a) substantial comorbidities; b) contraindication(s) for any platinum-doublet chemotherapy * Representative formalin-fixed paraffin-embedded (FPPE) tumor tissue block obtained during course of disease (archival tissue) or at screening * Participants with treated, asymptomatic central nervous system (CNS) metastases are eligible, provided they meet all of the following criteria: Measurable disease outside CNS; Only supratentorial and cerebellar metastases allowed; No ongoing requirement for corticosteroids as therapy for CNS disease; No stereotactic radiation within 7 days or whole-brain radiation within 14 days prior to …