High-Grade Gastroenteropancreatic Neuroendocrine Neoplasms. Modern Classification, Diagnostics and Treatment

Abstract

Poorly differentiated gastroenteropancreatic neuroendocrine neoplasms (GEP NENs) are rare malignancies, most of which are characterized by aggressiveness, a tendency to rapid metastasis and an unfavorable prognosis even when localized. In 2017 World Health Organization (WHO) updated classification of GEP NENs and recognized the category of well-differentiated pancreatic NET G3, associated with Ki‑67 index usually over 20%. The upper level of Ki‑67 is not defined. Usually it is 55%. Highgrade poorly differentiated pancreatic NENs are defined as pancreatic neuroendocrine carcinomas (panNECs). Although the NET G3 category is recognized for pancreatic neuroendocrine neoplasms only, many specialists consider it reasonable to apply this term to all well-differentiated GEP NETs with Ki‑67 index in the 20 to 55 percent range. Clinical behavior and therapeutic approaches for advanced GEP NECs and NETs G3 are different. Standard palliative chemotherapy for GEP NECs consists of cisplatin or carboplatin combined with etoposide. The second-line regimens include irinotecan-, oxaliplatin, fluoropyrimidine- and temozolomide-based regimens. Temozolomide-based chemotherapy regimens, as well as targeted therapy are more preferable as first line therapy for patients with NETs G3. The platinum-based chemotherapy regimens are considered at the time of disease progression. Further clinical studies with the inclusion of much more patients will determine the optimal treatment strategy for this category of patients.