Inclusion Criteria:  Histologically or cytologically documented, well differentiated, locally advanced or metastatic NETs The patient or parent/legal guardian (as appropriate) is willing and able to provide informed consent, and where required, the patient is willing to provide assent ≥12 years of age In the opinion of the patient's treating physician, other treatment options or clinical trials in this indication are unsuitable Patient has adequate bone marrow and organ function Urine dipstick ≤1+ for proteinuria or ≤30 mg/dL in urinalysis, ECOG ≤2 for adult patients (≥18 years of age), Karnofsky ≥60 for patients >16 and <18 years of age, and Lansky ≥60 for pediatric patients ≤16 years of age For female patients of childbearing potential and male patients with partners of childbearing potential, agreement (by patient and partner) to use a highly effective form(s) of contraception  Exclusion Criteria:  Uncontrollable hypertension, as defined by local institution Gastrointestinal disease or condition that the physician suspects may affect drug absorption History or presence of a serious hemorrhage Clinically significant cardiovascular disease Brain metastases and/or spinal cord compression untreated with surgery and/or radiotherapy High risk of bleeding at screening due to tumor invasion Arterial thrombosis or deep venous thrombosis within 6 months prior to first dosing or thromboembolic events (including stroke and/or transient ischemic attack) within 6 months prior to first dosing Received treatment with anticancer therapy, including investigational therapy, within 7 days or 5 half-lives (whichever is longer) Received prior treatment with surufatinib Inability to take medication orally Any other clinically significant comorbidities that, in the judgment of the treating physician, could predispose the patient to safety risks