Impact of Peritoneal Metastasis on Survival of Patients With Small Intestinal Neuroendocrine Tumor.

The liver and peritoneum are the 2 most common distant metastatic sites for small intestinal neuroendocrine tumors (SI-NET). In this study, we evaluated the differential impact of hepatic and/or peritoneal metastasis on prognosis of SI-NET patients. Surgical Pathology archives were searched for SI-NET resections performed between January 1, 1994 and August 31, 2017. Two hundred nineteen cases with clinical follow-up data were identified. Pathology reports and electronic medical records were reviewed. The 219 patients included 104 females and 115 males with a median age of 59 years (range, 19 to 85 y). There were 71 (33%) cases without hepatic or peritoneal metastasis, 80 (37%) with hepatic metastasis only, 14 (6%) with peritoneal metastasis only, and 53 (24%) with both hepatic and peritoneal metastasis at the time of surgery or during follow-up. The number of primary tumors, largest tumor size, lymph node metastasis, pT category, and sex were not significant independent prognostic factors in multivariate Cox proportional hazard regression. Age was the only variable other than presence of metastatic disease that was associated with worse prognosis (5% increase in risk/year of age; 95% confidence interval, 1.7%-8.2%; P=0.003). After controlling for patient age, pairwise comparisons of marginal linear predictions showed increased risk with peritoneal metastasis, with or without associated hepatic metastasis, compared to hepatic metastasis only. In conclusion, although limited by the number of patients with peritoneal metastasis only, these results support substratifying patients with metastatic SI-NET by anatomic site of metastasis.