Surufatinib Combined With Chemo Versus Surufatinib in the Treatment of Pulmonary Neuroendocrine Tumors

The goal of this clinical trial is to investigate if chemotherapy works with surufatinib to treat pulmonary neuroendocrine tumors. It will also learn about the safety of this combination regimen. The main questions it aims to answer are: Does chemotherapy combined with surufatinib could bring more survival benefits (ie. higher response rate or longer survival time) for patients with pulmonary neuroendocrine tumors? Is this combination regimen safe? Researchers will compare chemotherapy plus surufatinib with surufatinib monotherapy to see if this combination regimen works to treat pulmonary neuroendocrine tumors. Participants will: Take chemotherapy(Etoposide+Carboplatin, EC or Capecitabine+Temozolomide, CAPTEM) plus surufatinib or surufatinib monotherapy every 3 or 4 weeks as a cycle. Visit the clinic once every cycle for checkups and tests. Tumor assessment is performed every 2 cycles. Treatment will continued until disease progression, death, intolerable toxicity, or withdrawn.