Risk Factors and Prognosis of Peritoneal Metastases in Small Bowel Neuroendocrine Tumor Patients

Peritoneal metastases (PM) are common in small bowel neuroendocrine tumors (SBNETs). Risk factors for PM and their impact on disease prognosis is poorly studied.

This study reviews 20 years of experience with SBNETs, focusing on identifying risk factors for PM and the long-term oncologic outcomes of cytoreduction.

A retrospective single institutional study was performed from 2005 to 2024 identifying patients with SBNETs who underwent operative resection of their tumors. Primary endpoints were overall survival and progression-free survival, assessed with the Kaplan-Meier method.

In total, 396 patients were included in the study with rates of metastatic disease and PM of 71.7 and 30.1%, respectively. The presence of liver metastases, female sex, higher T stage, and elevated pancreastatin levels were associated with an increased risk of PM. By Kaplan-Meier analysis, patients with PM had worse overall survival (109 vs. 169 months; p = 0.01) and progression-free survival (42 vs. 75 months, p <0 .01) than those without PM; however, on multivariable analysis, these were not significant. Patients who received cytoreduction of PM had higher rates of major complications (i.e. Clavien-Dindo 3 or 4) than those who did not. Additionally, patients with PM had higher rates of postoperative bowel obstruction, although the greater use of peptide receptor radionuclide therapy in this population may also have contributed.

Peritoneal metastases are common in SBNET. Aggressive surgical management is associated with favorable long-term survival, which suggests it should be considered.