Therapeutic index of lymphadenectomy among patients with pancreatic neuroendocrine tumors: A multi-institutional analysis

Background The benefit derived from lymph node dissection (LND) in patients with pancreatic neuroendocrine tumors (pNETs) based on clinicopathological characteristics remains unclear. Methods Patients undergoing surgery for pNET between 1997 and 2016 were identified using a multi-institutional dataset. The therapeutic index of LND relative to patient characteristics was calculated. Results Among 647 patients, the median number of lymph nodes (LNs) evaluated was 10 (interquartile range: 4-16) and approximately one quarter of patients had lymph node metastasis (LNM) (N = 159, 24.6%). Among patients with LNM, 5-year recurrence-free survival was 56.0%, reflecting a therapeutic index value of 13.8. The therapeutic index was highest among patients with a moderately/poorly-differentiated pNET (21.5), Ki-67 >= 3% (20.1), tumor size >= 2.0 cm (20.0), and tumor location at the head of the pancreas (20.0). Patients with >= 8 LNs evaluated had a higher therapeutic index than patients who had 1 to 7 LNs evaluated (>= 8: 17.9 vs 1-7: 7.5; difference of index: 11.4). Conclusion LND was mostly beneficial among patients with pNETs >2 cm, Ki-67 >= 3%, and lesions located at the pancreatic head as identification of LNM was most common among individuals with these tumor characteristics. Evaluation of >= 8 LNs was associated with a higher likelihood of identifying LNM as well as a higher therapeutic index, and therefore this number of LNs should be considered the goal.