Study to Compare Capecitabine Combined With Dacarbazine(CAPDTIC) Versus Capecitabine Combined Temozolomide(CAPTEM) in Advanced and Metastatic Gastrointestinal Pancreatic and Esophageal Neuroendocrine Tumor

Inclusion Criteria: 1. sign written informed consent form 2. age ≥ 18 years 3. pathologically confirmed well-differentiated neuroendocrine tumor; 4. No prior antitumor treatment of capecitabine, dacarbazine or temozolomide. For recurrent patients after radical surgery, adjuvant chemotherapy should not include capecitabine, dacarbazine or temozolomide, and the last date should beyond 6 months prior to randomization; 5. At least 1 measurable lesion (only 1 measurable lymph node lesion is excluded) (routine CT scan \>=20mm, spiral CT scan \>=10mm, no prior radiation to measurable lesions); 6. Screening laboratory values must meet the following criteria (within past 7 days): hemoglobin ≥ 9.0 g/dL; neutrophils ≥ 1500 cells/ μL; platelets ≥ 100 x 10\^3/ μL; total bilirubin ≤ 1.5 x upper limit of normal (ULN); aspartic transaminase (AST) and alanine transaminase (ALT) ≤ 2.5 x ULN without, and ≤ 5 x ULN with hepatic metastasis; serum creatinine ≤1╳ULN; 7. KPS ≥ 70; 8. Predicted survival \>=3 months; 9. Negative serum or urine pregnant test within 7 days prior to randomization for child-bearing age women; 10. Sexually active males or females willing to practice contraception during the study until 30 days after end of study. Exclusion Criteria: 1. Hypersensitivity to capecitabine, dacarbazine or temozolomide; 2. Prior antitumor therapy (including corticosteroids and immunotherapy) or participation in other clinical trials within past 4 weeks, or have not recovered from toxicities since the last treatment; 3. Received surgery within past 4 weeks, or have not recovered from surgery; 4. Severe diarrhea; 5. Concurrent severe infection； 6. Severe, uncontrolled medical condition that would affect patients' compliance or obscure the interpretation of toxicity determination or adverse events, including severe liver disease (active hepatitis, cirrhosis), uncontrolled diabetes or hypertension, or pulmonary disease ( interstitial pneumonia, obstructive pulmonary disease or symptomatic bronchospasm); 7. Prior long term steroid therapy (excluding short term steroid treatment which is completed prior to \> 2 weeks of study enrollment)； 8. Meningeal carcinomatosis; 9. Patients with central nervous system(CNS) disorder or peripheral nervous system disorder or psychiatric disease； 10. Known history of uncontrolled or symptomatic angina, uncontrolled arrhythmias and hypertension, or congestive heart failure, or cardiac infarction within 6 months prior to study enrollment, or cardiac insufficiency； 11. Pregnant or nursing, or sexually active males or females refuse to practice contraception during the study until 30 days after end of study; 12. History of other malignancy. However, subjects who have been disease-free for 5 years, or subjects with a history of completely resected non-melanoma skin cancer or successfully treated in situ carcinoma, are eligible； 13. Person with no capacity (legally) or inappropriate to continue study treatment for ethics/medical reasons； 14. Underlying medical condition that, in the Investigator's opinion, would increase the risks of study drug administration or obscure the interpretation of toxicity determination or adverse events.