Study Evaluating the Efficacy of the myDIET Software Tool in the Nutritional Management of Patients With Localized and Resectable Gastric or Esogastric Junction Cancer.

The tool is based on self-questionnaires completed by the patient. They are mainly filled in using visual analogue scales (from 0-10) or grades of symptoms/toxicities (Grades 0 to 4), based on the CTCAE V5. These scales will cover the following themes: food intake, weight changes, digestive symptoms, taste disorders, pain and fatigue. The system will be able to monitor data changes and the response given will be adapted according to the severity of symptoms: * No signs of seriousness: general prevention or treatment documents/advice: toxicity management, nutritional advices targeted on symptoms, on digestive problems, on appropriate physical activity. * Presence of signs of seriousness: action to be taken and alert to the coordinating nurse, oncologist or dietician. In case of an alert, the coordinating nurse will call the patient back and either manage the symptom, schedule a nutritional consultation to initiate nutritional management, or refer the patient to the oncologist.