Endocrine Abstracts

Introduction: Until recently, lymph node metastases (LNM) in small bowel neuroendocrine tumours (SB-NETs) were classified as absent (N0) or present (N1). However, the American Joint Committee on Cancer (AJCC) updated the classification to N0, N1 (<12 positive lymph nodes), and N2 (≥12 positive LNM and/or a large mesenteric mass (MM) ≥2 cm). This updated N-classification has not been evaluated in a real-world population of patients with SB-NETs. The aim of this study is to describe the prevalence of N1 and N2 in patients with SB-NETs and explore its association with recurrence-free survival (RFS) and overall survival (OS).

Methods: A single-centre retrospective study was performed, including all patients with a curative SB-NET resection. Histology reports were reviewed and reclassified using the new AJCC N-classification. Demographic data were collected from patient records. RFS was calculated from the histology date to the date of disease recurrence, and OS was calculated from the histology date until death from any cause.

Results: A total of 112 patients (52% male, median age 63.5 years) were included. Sixty-seven patients (60%) had N1-disease, 45 patients (40%) had N2-disease. Among the N2-group, n = 35 (79%) had a MM ≥2cm, n = 8 (17%) had ≥12 positive LNM, and n = 2 (4%) met both criteria. The median MM size in N2-group was 30mm. Recurrence occurred in 18 patients (26.9%) in the N1-group and in 17 (38.6%) in the N2-group. No significant difference in recurrence time was found between N1-group (83 months) and N2-group (61 months), p-value 0.29. There was no significant difference (p-value 0.16) in OS between N1-group (134 months) and N2-group (106 months). However, patients with MM ≥2cm had significantly shorter OS (102 months, P = 0.006), compared to patients with MM ≤2cm (median not reached). Multivariate analysis suggested MM ≥2cm points towards significant worse OS (HR 3.71, P = 0.06).

Conclusion: For patients with SB NETs N1 or N2 LNM do not affect RFS or OS, but MM ≥2cm points towards worse OS. This highlights the need for tailored surveillance, particularly for patients with larger MMs. Future multi-center studies are needed to clarify the impact of N1 and N2 LNM on survival outcomes.