1. Principle of internal medicine treatment: Internal medicine treatment is divided into two parts: symptom control and anti-proliferation. Symptom control is mainly symptomatic treatment to relieve the symptoms caused by tumor hormone secretion; while anti-proliferation mainly includes biological therapy, targeted drugs to therapy and chemotherapy. For G1/G2 patients, drugs should be selected according to the size of their tumor load and the aggressiveness of the tumor, and for slow-growing tumors with a small load, even watchful waiting is an option. For G3 patients, chemotherapy-based treatment should be actively adopted. In conclusion, individualized treatment plan should be formulated by integrating the primary focus, metastatic site and the above characteristics. 2. Symptom control: Growth inhibitor analogues (SSA) and biological therapy with interferon can be preferred for symptom control. For example, PPI can be used to inhibit gastric acid secretion in gastrinoma, adrenal blockers such as ketoconazole or methylphenidate can be used to treat Cushing’s syndrome caused by ACTH tumor, diazoxide can be used to control insulin secretion in insulinoma, and verapamil, phenytoin and glucocorticoids can also be chosen. In addition, local treatment (such as liver intervention or radiofrequency treatment) can also achieve a better effect of controlling symptoms. 3, anti-proliferative: anti-proliferative drugs include: biological therapy, targeted drugs and chemotherapy. First, the pathological grading should be clarified. For G1/G2 patients, if the tumor load is relatively small and the growth is slow, the treatment of growth inhibitor analogues can be considered. If the tumor load is large or growing very rapidly, chemotherapy should be considered first, while targeted drugs can be considered for cases in between. For patients with G3, chemotherapy should be the mainstay, i.e. etoposide, irinotecan, platinum, temozolomide, fluorouracil, bevacizumab, etc. are all available options. Combination SSA therapy may also be considered for patients with positive octreotide imaging. SSA can be used in all GEP-NETs and is characterized by low side effects, good patient tolerance, and can be used in patients with poor general condition, poor organ function, or advanced age. It can be used in patients with poor general condition, poor organ function or advanced age, and it can be considered to increase the dosage or shorten the duration of dosing when the tumor tends to progress, and it can still achieve the effect of continuing to control tumor growth in some patients. Interferon is currently not used much in China, either alone or in combination with octreotide, but is usually used for second-line treatment and beyond. Biologic therapy is generally less effective (<10%), but is better tolerated by patients. Chemotherapy: Chemotherapy is mainly applied to pNETs, metastatic foregut NETs and NECs, while the efficacy of chemotherapy for NETs in the midgut remains to be further investigated. For pNETs, urostreptomycin ± fluorouracil is the preferred regimen abroad, but since this drug is not available in China, the commonly used regimen for G2 NETs is temozolomide ± capecitabine, which is not yet supported by large-scale clinical studies, but several small sample studies have confirmed that especially in pNETs, a high tumor remission rate (up to 70%) can be achieved, and PFS can up to 18 months. There are no validated markers to screen patients for temozolomide ± capecitabine, and this regimen may be tried in GI-NETs who have failed standard therapy. For NECs, platinum-based regimens (EP or IP) are recommended in the first line, while temozolomide + capecitabine ± bevacizumab is considered in the second line, in addition to steroids and oxaliplatin-based regimens. Targeted therapies: Targeted agents include sunitinib and everolimus, which are currently approved for pNETs only, both of which have been shown to be effective in large phase III clinical studies, with PFS of nearly 1 year. Although the efficiency of targeted drugs did not exceed 10%, the proportion of tumor shrinkage after treatment was significantly higher than that of the placebo group. The use of RECIST criteria for evaluating the efficacy of targeted drugs is still controversial, and a more scientific evaluation system to assess the efficacy of targeted drugs is expected to be introduced in the future. For GI-NETs that fail standard treatment, the regimen of everolimus ± SSA can be considered.