Eligibility Criteria:
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.