This is a single arm phase II study, in which 2 cycles of chemotherapy (5FU/CDDP) and immunotherapy (durvalumab and tremelimumab) are administered every 3 weeks with concurrent radiotherapy for inoperable locally advanced esophageal squamous cell carcinoma. Four weeks after completion of CCRT combined with immunotherapy, 2 cycles of durvaluma and tremelimumab will be administered every 4 weeks and thereafter durvalumab monotherapy Q4W will be maintained until unacceptable toxicity or disease progression, or for maximum 2 years after enrollment.

Inclusion Criteria:

• Histologically confirmed squamous esophageal cancer
• The clinical stage T2-3N0M0 or T1-3N1-3M0
• Inoperable case: it refers to medically inoperable status and/or patient's refusal to surgery and/or cervical location and/or locoregionally recurrent tumor after primary surgery
• ECOG PS of 0 to 1

Exclusion Criteria:

• clinical T4 disease (for example, invasion to aorta, vertebral body, or trachea/bronchus) or distant metastasis (M1)
• previously received radiotherapy for esophageal cancer