Study Evaluating Neurotoxicity in Patients With Metastatic Gastro Intestinal Cancer Taking Phycocare® or Placebo During Oxaliplatin Based Chemotherapy

Inclusion Criteria: * Male or female with the age \> or = to 18 years old. * Negative pregnancy test for women with child-bearing potential if applicable (without hysterectomy for example) * Information given to the patient who must have signed informed consent * Patient with Histologically or cytologically proven gastro intestinal cancer including oesogastric, colo-rectal, pancreatic cancers, locally advanced pancreatic cancers and planned to be treated with oxaliplatin * Patient with metastatic disease not previously treated * Patient willing not to take any plant-based therapy during the study (including phytotherapy and gemmotherapy) * Previous radiotherapy is authorized if discontinued ≥15 days prior to randomization * Sites of disease evaluated within 42 days prior C1 day 1 of chemotherapy with thoracic-abdominal-pelvic CT scan (or abdominal-pelvic MRI and chest X-ray) * Patient with ECOG Performance status 0 or 1 * Patients with a Life expectancy ≥12 weeks * Laboratory results: Hematologic function: polynuclear neutrophils ≥ 1.5.109/L platelets ≥100.109/L haemoglobin ≥9 g/dL Hepatic function: transaminases ≤2.5 times upper limit of normal (ULN) (≤5 ULN in case of hepatic metastases), alkaline phosphatases ≤2.5 x ULN (≤5 ULN in case of hepatic metastases), total bilirubin ≤1.5 x ULN Renal function: creatinemia clearance \>50 ml/min (Cockcroft and Gault) \- Patient with Public Health insurance coverage Exclusion Criteria: * Patients with phenylketonuria * Patients with known meningeal or brain metastases * Patient previously treated for their metastatic cancer * Patient previously treated with oxaliplatin * Patient with specific contraindication or known hypersensitivity to spirulina * Patient with specific contraindication or known hypersensitivity to oxaliplatin. * Known allergy or hypersensitivity to antibodies or any preservatives if patient is treated with a monoclonal antibody combined to chemotherapy (bevacizumab or cetuximab or panitumumab or nivolumab or Trastuzumab For patients treated with trastuzumab : patient without HER2 overexpression (defined by positive IHC3 or positive IHC2 and confirmed by a positive FISH result) * Patient with clinically significant coronaries affection or myocardial infarction within 6 months prior to randomization. * Patient with peripheral neuropathy \>1 (CTCAE scale version 5.0). * Patients with known dihydropyrimidine dehydrogenase (DPD) deficiency. * Patient with acute intestinal obstruction or sub-obstruction, history of inflammatory intestinal disease or extended resection of the small intestine or presence of a colic prosthesis. * Patient with unhealed wound, active oesogastric or duodenal ulcer, or bone fracture * Patient with an history of abdominal fistulas, trachea-esophageal fistulas or any other grade 4, gastro-intestinal perforations or non-gastrointestinal fistulas or intra-abdominal abscesses during the 6 months before randomization. * For patient treated with bevacizumab: patient with uncontrolled arterial hypertension (systolic pressure \>150 mmHg and/or diastolic pressure \>100 mmHg) with and without antihypertensive medication. Patients with high hypertension are eligible if antihypertensive medication lowers their arterial pressure to the level specified by the criterion. * Patient with an history of hypertensive crisis or hypertensive encephalopathy * Patient with other concomitant malignancy or history of cancer (except in situ carcinoma of the cervix, or non-melanoma skin cancer, treated with curative intent treatment) except if considered in complete remission for at least 2 years before randomization * Existence of any other pathology, metabolic problem, anomaly during the clinical examination or biological anomaly which may reasonable suspect an underlying pathology which would contra- indicate the use of the study medication or any other risk of complication related to the treatment. * Any treatment including an experimental drug, or participation in another clinical trial within 28 days before randomization. * Pregnant women, or women who could possibly be pregnant (or who expect to fall pregnant within 6 months of the end of treatment), or who are breast feeding are not eligible. * Men and women of child-bearing potential who do not accept to use a highly effective contraceptive (as per currently acceptable institutional standards) or abstinence during the study and for the month after the last administration of the study treatments. * Persons deprived of liberty or under guardianship. * Psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule.