Association of Radiochemotherapy and Immunotherapy for the Treatment of Unresectable Oesophageal caNcer

This study aims to assess the efficacy of durvalumab in combination with radiochemotherapy (FOLFOX and IMRT) and then as maintenance therapy for treating patients with localised unresectable oesophageal cancer. This is a randomized, French national, multicentre, comparative phase II trial

ARION study will randomize 120 patients, in 12 centers in France, according to a ratio 1:1 in the following arm of treatment: \- Standard and experimental arm: Definitive modulated-intensity radiotherapy will be delivered according to boost integrated technique 5 days a week for 5 weeks at a dose of: * 50 Gy delivered in 25 fractions to the macroscopic disease (endoscopic, TDM and fused FDG PET) * 45 Gy to the adjacent peri tumoral mucosis and prophylactic lymph node FOLFOX 4 simplified protocol, 1 infusion every 2 weeks (q2w) during 3 months starting with radiotherapy (+/- 1 day): * IV oxaliplatin 85 mg/m² in 2 h on day 1 (D1) * IV Leucovorin 200 mg/m² in 2 h on D1, followed by * IV 5-FU 400 mg/m² in 10 minutes on D1 followed by * IV continuous infusion 5-FU 2400 mg/m² in 46 h * Experimental arm: Concomitant administration of durvalumab: Every 4 weeks during concurrent FOLFOX (dose: 1500 mg) and after FOLFOX completion (total of 12 months of treatment).