Testing the Addition of a New Immunotherapy Drug, Atezolizumab (MPDL3280A), to the Usual Chemoradiation (CRT) Therapy Treatment for Limited Stage Small Cell Lung Cancer (LS-SCLC)

Inclusion Criteria: * Pathologically (histologically or cytologically) proven diagnosis of limited stage small cell lung cancer (Stage Tx, T1-T4, N0-3, M0, American Joint Committee on Cancer \[AJCC\] staging, 8th edition \[Ed.\]), within 60 days prior to registration * Patients must have received one cycle of platinum/etoposide chemotherapy pre-registration (prior to study entry). Study registration must be within 21 days from day 1 of the pre-registration cycle of chemotherapy. * Patients must have had measurable disease (per Response Evaluation Criteria in Solid Tumors \[RECIST\], version 1.1) prior to the required pre-registration cycle of platinum/etoposide chemotherapy * Minimal staging requirements include: * History/physical examination within 30 days prior to registration * Positron emission tomography (PET)/computed tomography (CT) scan for staging within 60 days prior to registration * CT chest and CT abdomen with IV contrast (unless contraindicated based on kidney function) within 60 days prior to registration; magnetic resonance imaging (MRI) abdomen with IV contrast allowed in place of CT abdomen * Note: If contrast allergy exists, premedication per institutional guidelines should be performed prior to obtaining CT with contrast. The only exception to this is a documented life-threatening allergy * MRI scan of the brain with contrast (preferred) or CT scan of the brain with contrast (allowable if there is a contraindication with MRI with contrast) …