Prognostic Assessment of Non-functioning Neuroendocrine Pancreatic Neoplasms as a Basis for Risk-Adapted Resection Strategies.

ABSTRACT

BACKGROUND: In contrast to exocrine pancreatic carcinomas, prognosis and treatment of pancreatic neuroendocrine neoplasms (PNEN) are significantly different. The variable growth pattern and associated clinical situation of functioning and non-functioning PNEN demand an individualized surgical approach. However, due to the scarce evidence associated with the rare disease, guidelines lack detailed recommendations for indication and for the required extent of surgical resection. METHODS: In a retrospective single-center study from 1990 to 2018, 239 patients with PNEN were identified. Clinical data were collected in the MaDoc database of the University Medical Center Mainz. A total of 155 non-functional PNEN were selected for further analysis. RESULTS: According to the classification of NET by the WHO in 2017, 28.8% (n = 40) of the tumors were G1, 61.9% (n = 86) G2, and 9.4% (n = 13) G3. In 73 patients, hepatic metastases were present. Sixty patients had lymph node metastasis. An R0 resection was achieved in 98 cases, an R1 situation in 10 cases. Five times, a tumor debulking was carried out (R2) and 5 times the operation was aborted without any resection because of the advanced tumor stage. A relapse occurred in 29 patients. Different prognostic factors (grade, tumor size, age) were analyzed. Grade-dependent 10-year overall survival rates were 79.5% (grade 1) and 60.1% (grade 2), respectively. The survival rate of grade 3 patients was limited to 66.7% after 13 months. CONCLUSION: In our study, patients with non-functioning PNEN had a longer overall survival after successful R0 resection. The risk analysis confirmed a Ki-67 cutoff value of 5%, which divided a high- and low-risk group. Patients with a PNEC G3 (Ki-67 index > 50%) had a very poor prognosis.