Assessment of the Efficacy of Bevacizumab in Combination With Folfiri as Second-line Treatment in Patients Suffering From an Advanced Inoperable Poorly Differentiated Neuroendocrine Carcinoma of an Unknown or Gastroentero-pancreatic Primary Cancer

Inclusion Criteria: * Man or woman aged ≥ 18 years old, * Poorly differentiated neuroendocrine carcinoma (NEC) from a gastrointestinal tract (from esophagus to anal canal) and biliopancreatic primary or an unknown primary cancer, locally advanced and/or metastatic, * Centralized review of the diagnostic by a consulting pathologist specializing in NET (TENPATH network), * Recommendation of a second-line chemotherapy after progression, documented using the RECIST criteria v.1.1, and after a first-line chemotherapy treatment by cisplatin (or carboplatin) + etoposide or in the event of progression in the 6 months following the discontinuation of this first-line treatment, * Recommendation of a second-line chemotherapy for the refractory patient or contraindicated for platinum-etoposide chemotherapy * Patients presenting at least one measurable target lesion according to the RECIST criteria v.1.1, in an area not previously irradiated, * General condition ≤ 2 (WHO), * Patient of child bearing age accepting to use an effective contraception during treatment and until 6 months after the last administration, * Patient who signed the informed consent form. Exclusion Criteria: 1. Relating to the tumor, the patient, and previous treatment: * Well differentiated neuroendocrine tumor * Mixed tumor, except if the NEC component is \> 70%, the patient is eligible, * First-line chemotherapy other than cisplatin (or carboplatin) and etoposide, * All malignant disease in the three years before randomization, with the exception of basal cell carcinoma or in situ cancer treated for curative purposes, * A pregnant or breastfeeding woman, * Lack of efficient contraception (for men or women of reproductive age), * All medical, geographical, social, and psychological conditions or a legal situation that will not allow the patient to finish the study or sign an informed consent form, 2. Relating to the chemotherapy (Folfiri): * Any of the following uncontrolled progressive diseases in the 6 months before randomization: liver failure, renal insufficiency, respiratory distress, congestive heart failure (NYHA III-IV), unstable angina, myocardial infarction, significant arrhythmia, * Known deficiency in dihydropyrimidine dehydrogenase, * Known Gilbert's syndrome, * Total bilirubin level \>1.5x the upper limit of normal (ULN); AST (Aspartate transaminase) and/or ALT (Alanine transaminase) \>5x ULN; TP \<50%; * Neutrophils \<1.5x109/l, platelets \<100x109/l, hemoglobin \<9 g/dl, * Chronic uncontrolled diarrhea, unresolved intestinal occlusion or subocclusion, * History of anaphylactic reaction or known intolerance to atropine (sulfate) or to loperamide or to antiemetics administered in association with Folfiri, * All treatment with concomitant anticonvulsive agents, CYP3A4 inducers (phenytoin, phenobarbital, carbamazepine), discontinued for at least 7 days, 3. Relating to bevacizumab: * Uncontrolled brain metastases (by local treatment), * All uncontrolled progressive disease within 1 month prior to randomization: grade 3-4 gastrointestinal bleeding (peptic ulcer, erosive esophagitis or gastritis), infectious disease or intestinal inflammation, diverticulitis, pulmonary embolism or other uncontrolled thromboembolic event, * Uncontrolled high blood pressure defined as a systolic blood pressure \>140 mmHg or diastolic pressure \>90 mmHg, * Patients receiving anticoagulant treatment with an unstable dose of a vitamin K antagonist treatment, and/or having an abnormal INR (\>3) in the four weeks before the randomization, * Verified proteinuria above or equal to 1g/24 hours measured from 24 hours of urine if the urinary protein dipstick control is above or equal to 2+, * Creatinine clearance (MDRD) \<50 ml/min. * Hypersensitivity to the active substance or to any of the excipients. * Hypersensitivity to Chinese Hamster Ovary (CHO) cell products or other recombinant human or humanised antibodies.