Size Under Scrutiny: Preoperative Imaging Size of Mesenteric Deposits Does Not Predict Oncological Outcomes in Small Intestinal Neuroendocrine Tumors

Background Small intestinal neuroendocrine tumors (SiNETs) are rare tumors with propensity to cause bulky fibrotic mesenteric masses by hematogenous and lymphatic invasion. They exhibit variable oncological behavior and reliable prognostic markers remain elusive. The 8 th edition American Joint Commission on Cancer introduced mesenteric mass ≥2 cm to improve prognostication. The clinical utility in prognostication remains unknown. We reviewed outcomes of resected SiNETs to determine if computed tomography (CT) size is associated with oncological outcomes. Methods Retrospective review of resected SiNET patients at two tertiary centers with evaluable preoperative CT scans. Measured the largest diameter of the mesenteric mass and the cutoff of 2 cm used to correlate with oncological outcomes. Results Seventy-three patients operated for SiNET with preoperative CT were included. The largest mesenteric mass was <2 cm in 28 and ≥2 cm in 45 patients. Cohorts were similar in demographic and clinical characteristics. Median follow-up was 47 months. Overall survival (OS) and progression free survival (PFS) were similar. No significant differences in estimated mean OS (136 vs 139 months, P = 0.981) or median PFS (90 vs 71 months, P = 0.126) for the <2 cm and >2 cm cohorts, respectively. Univariable analysis failed to show an association between mesenteric size as a continuous variable, and at the ≥2 cmcutoff. Age, cardiac comorbidities, and palliative intent surgery were the only factors that correlated with survival. Discussion Mesenteric mass size on preoperative CT was not correlated with oncological outcomes and by itself showed little utility in preoperative decision-making.