Alternative lengthening of telomeres and Ki-67 proliferation index provide complementary information on recurrence risk after resection of pancreatic neuroendocrine tumors.

Given the heterogeneous clinical behavior of pancreatic neuroendocrine tumors (pNETs), improved prognostic markers are needed to guide management and post-resection surveillance. Patients who underwent resection of large (≥3 cm) sporadic well-differentiated pNETs from 2000 to 2019 were identified. The Ki-67 proliferation index was determined using immunohistochemistry, and alternative lengthening of telomeres (ALT) status was assessed using fluorescence in situ hybridization. Recurrence-free and overall survival were estimated using Kaplan-Meier analysis. Multivariable Cox regression analysis evaluated factors associated with recurrence-free survival. A total of 106 patients were identified. ALT was positive in 57 (54%) and negative in 49 (46%). Ki-67 was ≥3% in 74 (70%) and <3% in 32 (30%). Tumors with Ki-67 ≥3% were more likely to be ALT positive (61% vs. 38%, p = .046). Stratifying by ALT status and Ki-67 proliferation index, median recurrence-free survival was 4.6 years for patients with ALT-positive/Ki-67 ≥3% tumors, 3.1 years for patients with ALT-positive/Ki-67 <3% tumors, 12.4 years for patients with ALT-negative/Ki-67 ≥3% tumors, and 20.2 years for patients with ALT-negative/Ki-67 <3% tumors (p < .001). Initial recurrence was distant in 82% and locoregional in 18%. Across all groups, overall survival was similar (p = .19). In multivariable analysis, advanced age, ALT positivity, perineural invasion, and lymph node metastases were associated with increased recurrence risk (all p < .05). ALT and Ki-67 provide complementary information on post-resection recurrence risk, which can guide subsequent surveillance and management strategies. These data support the incorporation of ALT testing into routine clinical practice.