Is there a prognostic difference between functional and nonfunctional islet cell tumors?

BACKGROUND: Pancreatic islet cell tumors are categorized as either functioning or nonfunctioning. Functioning islet cell tumors (FIT) elaborate a variety of hormones, producing dramatic symptoms, while the initial presentation of non-functioning islet cell tumors (NIT) is commonly an abdominal mass or symptom complex related to invasion of adjacent structures. As a result, NIT are purported to present at a later stage, with lower resectability rates, and an overall poorer prognosis, when compared to FIT. In addition, a number of reports have indicated that the incidence of NIT has increased significantly in recent years. PATIENTS AND METHODS: Twenty-eight patients were studied retrospectively. All had islet cell tumors of the pancreas and were seen at the University of Nebraska Medical Center and affiliated Nebraska Methodist Hospital during a 19-year period.
RESULTS: There were 9 patients (32%) in the NIT group and 19 (68%) in the FIT group. The mean ages at presentation were 61 years for the NIT and 52 years for the FIT group. In the NIT group, all presented with either abdominal pain (n = 7) or jaundice (n = 2). In contrast, over 90% of the patients with FIT had symptoms referable to the specific hormone elaborated by the tumor. Primary tumor size for NIT was 4.1 +/- 0.7 cm versus 5.0 +/- 0.6 cm for the FIT group. No significant difference was found for NIT versus FIT with respect to the incidence of metastatic disease at presentation (44% versus 53%), resectability rate with curative intent (44% versus 53%), or disease-free survival at 2 years (67% versus 40%).
CONCLUSIONS: This series, in contrast to earlier reports, suggests that nonfunctioning islet cell tumors do not present at a more advanced stage, have lower resectability rates, or an overall poorer long-term prognosis when compared to functioning tumors.