cyclophosphamide + cisplatin + streptozocin + vincristine

**Cyclophosphamide + cisplatin + streptozocin + vincristine** is a combination chemotherapy regimen consisting of four cytotoxic agents used primarily for the treatment of advanced neuroendocrine tumors, particularly pancreatic islet cell carcinomas and carcinoid tumors. Cyclophosphamide is an alkylating agent that cross-links DNA strands inhibiting cancer cell replication; cisplatin is a platinum-based alkylating-like agent that forms DNA adducts leading to apoptosis; streptozocin is a nitrosourea antibiotic that methylates DNA with selectivity for pancreatic beta cells; and vincristine is a vinca alkaloid microtubule inhibitor that disrupts mitotic spindle formation. This regimen leverages synergistic cytotoxicity across different phases of the cell cycle for antitumor activity in slowly proliferating neuroendocrine malignancies.