Condition: Small Cell Lung Cancer

The purpose of this study is to compare overall survival (OS) and progression free survival (PFS) per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) as assessed by blinded independent central review (BICR).

Hypothesis (H1): Concurrent chemoradiation therapy with pembrolizumab followed by pembrolizumab plus olaparib is superior to concurrent chemoradiation therapy alone with respect to PFS per RECIST 1.1 by BICR.

Hypothesis (H2): Concurrent chemoradiation therapy with pembrolizumab followed by pembrolizumab is superior to concurrent chemoradiation therapy alone with respect to PFS per RECIST 1.1 by BICR.

Hypothesis (H3): Concurrent chemoradiation therapy with pembrolizumab followed by pembrolizumab plus olaparib is superior to concurrent chemoradiation therapy alone with respect to OS.

Hypothesis (H4): Concurrent chemoradiation therapy with pembrolizumab followed by pembrolizumab is superior to concurrent chemoradiation therapy alone with respect to OS.