Endocrine Abstracts

Background: Rectal neuroendocrine tumours (r-NETs) are the second most common neuroendocrine tumours in the digestive tract, with increasing incidence due to improved colonoscopy and cancer screening. These small, yellowish, low-grade lesions are often found incidentally during colonoscopies and generally have a favourable prognosis, with median survival sometimes exceeding 30 years. However, up to 20% of r-NETs may be misdiagnosed during endoscopy, risking inadequate treatment. Prognosis is influenced by factors such as tumour size (with a ≥10 mm cutoff), grading, staging, and lymphovascular invasion, leading to guidelines recommending endoscopic resection for small, low-grade lesions. The study aims to evaluate the clinical outcomes of patients with r-NETs <10 mm after endoscopic resection.

Methods: A retrospective single-center study was conducted, including patients with rectal neuroendocrine tumours <10 mm after endoscopic resection. The primary endpoint was progression-free survival. Statistical analysis was performed using MedCalc® software, with a p-value <0.05 considered significant. The Cox proportional hazards regression model was used to identify risk factors for disease progression.

Results: Out of 81 patients considered, 68 (83.9%) were included after excluding 13 for various reasons. The final cohort included 40 males (58.8%) and 28 females (41.2%), with a median age of 53 years and a median tumour size of 5 mm. Most tumours were grade 1 (92.6%). Endoscopic resections were inadequate (biopsy forceps or cold/hot snare) in 42 cases (61.8%) and advanced (EMR, ESD, or TAMIS/TEMS) in 26 cases (38.2%). Positive resection margins were observed in 47% of cases, and lymphovascular invasion was present in 1.4%. Tumour recurrence (local in all cases) occurred in 3 patients (3.4%). The median progression-free survival was 33.5 months, and the median overall survival was 35.5 months (range: 1-170 months). Only two deaths (2.9%) were recorded, neither of which were tumour-related, occurring after a median of 81.5 months. No significant prognostic factors for tumour recurrence were identified.

Conclusion: R-NETs <10 mm generally exhibit non-aggressive behaviour. However, more extensive prospective studies are required to gain a comprehensive understanding of these rare and heterogeneous tumours.