Locoregional Progression and Surgical Indications in Stage IV Asymptomatic SI-NETs

Small intestinal neuroendocrine tumors are often diagnosed at an advanced stage, with up to 70 percent of patients presenting with stage IV disease. While some guidelines recommend prophylactic resection of the primary tumor and mesenteric lymph node metastasis in patients without abdominal symptoms at diagnosis to prevent future abdominal complications, the benefit of this approach remains uncertain. This retrospective cohort study included 44 asymptomatic patients with stage IV small intestinal neuroendocrine tumors treated at Uppsala University Hospital between 2014 and 2019. Additional 10 symptomatic patients who underwent at least two computed tomography scans prior to planned surgery were included in the analysis of mesenteric metastasis volume change and tumor growth rate. The primary outcomes were abdominal symptoms development requiring surgical intervention, and the assessment of mesenteric metastasis size progression. During a 10-year follow-up, only four initially asymptomatic patients (9%) developed symptoms leading to surgery. Among all 54 patients, the median volume change in mesenteric metastases was -298 mm 3 (IQR: -2785 − 1294), with no significant difference between baseline and most recent scans (p = 0.38). The median interval between scans was 29 months, and the median tumor growth rate was −0.6 % per month (IQR: -3.6 − 1.9 %). Similar results were observed in the asymptomatic group. These findings suggest that a non-operative management in stage IV patients without abdominal symptoms is associated with a low incidence of symptom development and limited progression of mesenteric metastases.