This is a Phase III, randomized, double-blind, placebo-controlled, multi-center international study to assess the efficacy and safety of durvalumab administered concurrently with dCRT in patients with locally advanced, unresectable esophageal squamous cell carcinoma (ESCC).

Approximately 600 patients with locally advanced, unresectable ESCC (AJCC 8th cStage II-IVA) will be randomized in a 2:1 ratio to receive either durvalumab + dCRT or placebo + dCRT. The primary objectives of this study are to assess the efficacy of durvalumab + dCRT compared with placebo + dCRT in terms of progression free survival (PFS, per RECIST 1.1 as assessed by BICR) in PD-L1 High population.

Inclusion Criteria:

• 18 years or older at the time of signing the ICF.
• Histologically or cytologically confirmed esophageal squamous cell carcinoma, and present with locally advanced disease (Stage II-IVA).
• Unresectable or refusing surgery, and has been deemed suitable for definitive chemoradiation therapy.
• Patients with at least an evaluable lesion per RECIST 1.1.
• Mandatory provision of available tumor tissue for PD-L1 expression analysis.
• ECOG PS 0 or 1.
• Adequate organ and marrow function.
• Life expectancy of more than 3 months.

Exclusion Criteria:

• Histologically or cytologically confirmed small cell esophageal carcinoma, esophageal adenocarcinoma or other mixed carcinoma.
• Prior anti-cancer treatment for ESCC.
• Patient with a great risk of perforation and massive bleeding.
• History of allogeneic organ transplantation.
• Active or prior documented autoimmune or inflammatory disorders.
• Uncontrolled intercurrent illness.
• History of another primary malignancy.
• Active infection including tuberculosis, hepatitis B, hepatitis C, or human immunodeficiency virus.
• Known allergy or hypersensitivity to any of the study drugs or any of the study drug excipients.

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal. All request will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA Pharma Data Sharing Principles. For details of our timelines, please rerefer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

When a request has been approved AstraZeneca will provide access to the de-identified individual patient-level data in an approved sponsored tool . Signed Data Sharing Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information. Additionally, all users will need to accept the terms and conditions of the SAS MSE to gain access. For additional details, please review the Disclosure Statements at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

Sponsor, excluding supply chain management personnel, will remain blinded.