Inclusion Criteria:

* Participant has provided informed consent before initiation of any study-specific activities/procedures.
* Age ≥ 18 years or ≥ legal age within the country if it is older than 18 years.
* Histologically or cytologically documented ES-SCLC (American Joint Committee on Cancer, 2017, Stage IV SCLC \[T any, N any, M1 a/b/c\]), or T3 to T4 due to multiple lung nodules that are too extensive or have tumor/nodal volume that is too large to be encompassed in a tolerable radiation plan.
* Measurable disease as defined per RECIST 1.1.
* Suitable to receive carboplatin, etoposide and durvalumab regimen as first-line treatment per investigator clinical assessment.
* Minimum life expectancy ≥ 12 weeks.

Exclusion Criteria:

* Participants can have no history of other malignancy in the last 2 years.
* Any symptomatic central nervous system (CNS) metastases, or leptomeningeal disease.
* They will have no history of severe or life-threatening events to immune-mediated therapy.
* History of arterial thrombosis (eg, stroke or transient ischemic attack) within 6 months prior to first dose of study treatment.
* They will have no active autoimmune or inflammatory disorders.
* Presence of active human immunodeficiency virus (HIV) or active Hepatitis (B/C) infection.
* Evidence or interstitial lung disease (ILD) or active, non-infectious pneumonitis.
* History of solid organ transplant.
* They will not have had a myocardial infarction and/or symptomatic congestive heart failure (New York Heart Association \> class II) within 6 months prior to first dose of study treatment.