Ovarian cancer is associated with undernutrition in more than half of all cases. The current management of undernutrition-cachexia in cancer is not specific. It is well recognized that the nutritional support currently offered to cancer patients is not effective in combating cachexia, which progresses inexorably, leading to the patient's death. It is therefore necessary to offer specific and adapted care, in particular by optimizing the quality of nitrogen intake. To achieve this, the investigators first need to define the specific amino acid requirements of cancer patients.

Inclusion Criteria:

• Histological diagnosis of high-grade serous ovarian cancer not immediately resectable (stage III or IVa) managed at Grenoble Alpes University Hospital.
• Affiliation to the French social security system.
• Able to understand and follow the instructions necessary for the conduct of the trial, and having given written consent for the study.

Exclusion Criteria:

• Significant active comorbidity requiring long-term drug treatment (e.g. organ failure, diabetes) or history of pathology likely to impact amino acid metabolism (e.g. urea or homocysteine cycle abnormalities, tyrosinemia, alkaptonuria, hyperprolinemia, organic aciduria).
• vegetarian or vegan diet
• difficult venous access
• Persons covered by articles L1121-5 to L1121-8 of the CSP (corresponding to all protected persons: pregnant women, parturients, nursing mothers, persons deprived of their liberty by judicial or administrative decision, persons subject to a legal protection measure).
• Subject receiving more than 4,500 euros in compensation for participation in other research involving the human body in the 12 months preceding this study.
• Significant biological abnormalities (not explained by the underlying pathology for women with ovarian cancer)
• Liver metastases