This is a prospective, randomized, open label study on the efficacy of octreotide lar as maintenance treatment after first-line chemotherapy for patients with unresectable or metastatic gastro-entero-pancreatic or esophageal neuroendocrine carcinomas.The patients with unresectable or metastatic GEP or esophageal NEC who got CR/PR/SD after chemotherapy with IP or EP regimen qualified with the inclusion criteria are enrolled. All the patients enrolled in our study will be randomly assigned to receive octreotide LAR (group A) as maintenance treatment or follow up (group B) to disease progression. Treatment will be discontinued on withdrawal of patient consent, disease progression, unacceptable toxicity, a treatment delay of >2 weeks, or major protocol violations, after which patients were followed up every 3 months for a minimum of 12 months.