Endocrine Abstracts

Background: Although gastroenteropancreatic neuroendocrine tumors G3 (GEP-NET G3) and neuroendocrine cancers (GEP-NEC G3) are characterized in histopathological examination by Ki67>20% or >20 mitoses/10HPF their management and prognosis is substantially different. Despite the WHO introduces the novel well-differentiated neuroendocrine tumour of high grade (NET G3) classification in 2017 the clinical management of them is still challenging due to high NET G3 heterogeneity and limited data in regards to best therapeutic strategies.

Material and Methods: We review clinical characteristics, treatment options, and outcomes in cohort of patients with gastroenteropancreatic NET G3 (GEP-NET) managed at our centre since implementation of the new WHO classification (2017 – 2021).

Results: There were 9 cases of GEP-NET G3 (4 women and 5 men, mean age at diagnosis 62,6 years, range 47-80 years). 8 of them had disease stage IV at diagnosis (with liver, lymph nodes, bone, adrenal, brain and peritoneal metastases) and 1 stage IIB with loco-regional lymph node metastasis. The tumours originate from: pancreas (3 cases), stomach (2 cases), small intestine (2 cases), large intestine (1 case) and in 1 case the primary site was unknown. Mean Ki67 was 35% (range 25-70%). In 4 cases there was good or very good somatostatin receptor expression (SSTR) (Kenning score 3 and 4) in somatostatin receptor imaging. Treatment options included combination of surgery, somatostatin analogues (SSA), Peptide Receptor Radionuclide Therapy (PRRT) or chemotherapy (temozolomide/capecitabine or platinum-based regimens). Mean overall survival was 17,2 months (range 3,0 - 46,6 months).

Conclusion: NET G3 management is challenging due to the their heterogeneity and relatively poor prognosis. Further research is needed to optimize/personalize NET G3 therapy with regard to differences in their organ of origin, stage, grading and SSTR expression status.