Endocrine Abstracts

Background: A metastatic mesenteric mass is a hallmark of small intestinal neuroendocrine tumours (SI-NETs). However, little is known about the evolution of a SI-NET-associated mesenteric mass over time.

Methods: Retrospectively, 530 patients with proven SI-NET and ≥2 available CT-scans were assessed for clinical characteristics at diagnosis and the presence and growth of a mesenteric mass on every consecutive CT-scan until end of follow-up or resection and in correlation with receiving Peptide Receptor Radionuclide Therapy (PRRT).

Results: A mesenteric mass was present in 64.2% of the patients of whom 13.5% showed growth of mesenteric mass according to RECIST 1.1. In patients without a mesenteric mass, only 2.6% showed growth of preexisting small nodule or development of new mesenteric mass. The median time to growth was 37.1 months. Independent predictors of growth were having a mesenteric mass (OR 8.14, 95% CI: 2.41–27.44, P=0.001) and male gender (OR 1.97, 95% CI: 1.03 – 3.75, P=0.04). Furthermore, of the patients treated with PRRT (n=132), only 4.4% had a reduction of their mesenteric mass according to RECIST 1.1.

Conclusion: Absence of a mesenteric mass at diagnosis of a SI-NET is associated with a low chance on development of a mesenteric mass over time. If present, we found that the hallmark dominant mesenteric mass in SI-NETs shows a highly inert behavior when assessed by RECIST 1.1 criteria and the only independent predictors of growth were having a mesenteric mass and male gender. Additional studies are needed to explore a possible role of sex steroids in the pathogenesis of SI-NET-associated mesenteric mass. Finally, shrinkage of the mesenteric mass after PRRT occurred in a small subset of patients, indicating a differential response to PRRT compared to other NET localizations.