Patients with documented disease progression following the first line chemotherapy (Arm B) may be eligible for crossover to be treated with dostarlimab, with the same schedule as arm A. conditions: Pancreatic Adenocarcinoma conditions: Ampulla of Vater Carcinoma conditions: Adrenocortical Carcinoma conditions: Neuroendocrine Carcinoma conditions: Soft Tissue Sarcoma conditions: Small Bowel Adenocarcinoma conditions: Duodenum Adenocarcinoma conditions: Gastric Adenocarcinoma studyType: INTERVENTIONAL phases: PHASE2 allocation: RANDOMIZED interventionModel: PARALLEL interventionModelDescription: Randomized, multicenter, comparative phase II trial primaryPurpose: TREATMENT masking: NONE count: 120 type: ESTIMATED name: Dostarlimab name: Chemotherapy measure: Progression-free survival measure: Objective Response Rate measure: Duration of response measure: Overall Survival measure: Progression-Free Survival 2 measure: Objective response rate 2 measure: Progression-Free Survival -crossover measure: Circulating tumor DNA level measure: Incidence of treatment-emergent adverse events measure: Quality of life questionnaire - Core 30 (QLQ-C30) sex: ALL minimumAge: 18 Years stdAges: ADULT stdAges: OLDER_ADULT facility: Institut de Cancérologie de l'Ouest city: Angers country: France name: Victor SIMMET, MD role: CONTACT lat: 47.46667 lon: -0.55 facility: Institut du Cancer Avignon-Provence city: Avignon country: France name: Clémence TOULLEC, MD role: CONTACT lat: 43.94834 lon: 4.80892 facility: CHU Jean Minjoz city: Besançon country: France name: Angélique VIENOT, MD role: CONTACT lat: 47.24878 lon: 6.01815 facility: CHU Morvan city: Brest country: France name: Pierre-Guillaume POUREAU, MD role: CONTACT lat: 48.3903 lon: -4.48628 facility: Centre François Baclesse city: Caen country: France name: Elodie COQUAN, MD role: CONTACT lat: 49.18585 lon: -0.35912 facility: Centre Jean Perrin city: Clermont-Ferrand country: France name: Florence OSAER-POLYCARPE, MD role: CONTACT lat: 45.77966 lon: 3.08628 facility: CHU - Henri Mondor city: Créteil country: France name: Christophe TOURNIGAND, MD role: CONTACT lat: 48.78333 lon: 2.46667 facility: Centre Georges François Leclerc city: Dijon country: France name: François GHIRINGHELLI, MD role: CONTACT lat: 47.31667 lon: 5.01667 facility: Centre Léon Bérard city: Lyon country: France name: Clélia COUTZAC, MD role: CONTACT lat: 45.74848 lon: 4.84669 facility: Hôpital la Timone city: Marseille country: France name: Laëtitia DAHAN, MD role: CONTACT lat: 43.29551 lon: 5.38958 facility: Institut Paoli Calmettes city: Marseille country: France name: Christelle DE LA FOUCHARDIERE, MD role: CONTACT lat: 43.29551 lon: 5.38958 facility: Institut de Cancérologie de Lorraine city: Nancy country: France name: Aurélien LAMBERT, MD role: CONTACT lat: 48.68439 lon: 6.18496 facility: Institut Mutualiste Montsouris city: Paris country: France name: Raphaël COLLE, MD role: CONTACT lat: 48.85341 lon: 2.3488 facility: CHU de Bordeaux - Hôpital Haut -Lèvêque city: Pessac country: France name: Denis SMITH, MD role: CONTACT lat: 44.81011 lon: -0.64129 facility: CHU de Poitiers city: Poitiers country: France name: David TOUGERON, MD role: CONTACT lat: 46.58333 lon: 0.33333 facility: Institut Jean Godinot city: Reims country: France name: Damien BOTSEN, MD role: CONTACT lat: 49.25 lon: 4.03333 facility: Centre Eugène Marquis city: Rennes country: France name: Héloïse BOURIEN, MD role: CONTACT lat: 48.11198 lon: -1.67429 facility: CHU de Rouen city: Rouen country: France name: Frédéric DI FIORE, MD role: CONTACT lat: 49.44313 lon: 1.09932 facility: Institut de Cancérologie de l'Ouest city: Saint-Herblain country: France name: Sandrine HIRET, MD role: CONTACT lat: 47.21765 lon: -1.64841 facility: CHU de Toulouse Hôpital Rangueil city: Toulouse country: France name: Rosine GUIMBAUD, MD role: CONTACT lat: 43.60426 lon: 1.44367 facility: Gustave Roussy Grand Paris city: Villejuif country: France name: Cristina SMOLENSCHI, MD role: CONTACT lat: 48.7939 lon: 2.35992 facility: Hôpital Saint-Antoine city: Paris state: Île-de-France country: France name: Thierry ANDRE, MD role: CONTACT lat: 48.85341 lon: 2.3488 hasResults: False