Alternative lengthening of telomeres in primary pancreatic neuroendocrine tumors is associated with aggressive clinical behavior and poor survival

Purpose: Alternative lengthening of telomeres (ALT), a telomerase-independent telomere maintenance mechanism, is strongly associated with ATRX and DAXX alterations and occurs frequently in pancreatic neuroendocrine tumors (PanNET). Experimental Design: In a Korean cohort of 269 surgically resected primary PanNETs and 19 sporadic microadenomas, ALT status and nuclear ATRX and DAXX protein expression were assessed and compared with clinicopathologic factors. Results: In PanNETs, ALT or loss of ATRX/DAXX nuclear expression was observed in 20.8% and 19.3%, respectively, whereas microadenomas were not altered. ALT-positive PanNETs displayed a significantly higher grade, size, and pT classification (all, P P P = 0.001) and the presence of lymph node ( P P = 0.002). Furthermore, patients with ALT-positive primary PanNETs had a shorter recurrence-free survival [HR = 3.38; 95% confidence interval (CI), 1.83–6.27; P P = 0.008). Similarly, tumors with loss of ATRX/DAXX expression were significantly associated with ALT ( P P P = 0.003). Conclusions: Both primary ALT-positive and ATRX/DAXX-negative PanNETs are independently associated with aggressive clinicopathologic behavior and displayed reduced recurrence-free survival. In contrast, ALT activation and loss of ATRX/DAXX are both associated with better overall survival in patients with metastases. Therefore, these biomarkers may be used as prognostic markers depending on the context of the disease. Clin Cancer Res; 23(6); 1598–606. ©2016 AACR .