Incidental Detection of Pancreatic Neuroendocrine Tumors: An Analysis of Incidence and Outcomes

Pancreatic neuroendocrine tumors (NETs) are increasingly discovered incidentally during radiologic or endoscopic examinations. The frequency of incidental detection is unknown. It is also unclear whether patients with incidentally discovered, early-stage, asymptomatic tumors should be treated similarly to patients who present with tumor-related symptoms. Patients with nonmetastatic pancreatic NETs treated at the H. Lee Moffitt Cancer Center between 1999 and 2010 were assigned a stage (I-III) on the basis of the new American Joint Committee on Cancer classification. The frequency of incidentally diagnosed tumors was evaluated and stratified by stage. Progression-free survival was measured by log rank testing to compare patients with incidentally detected versus symptomatic tumors. Multivariate analysis was performed controlling for other prognostic factors including tumor stage, grade, and location, and patient age. Among 143 patients with nonmetastatic pancreatic NETs, 56 patients (40%) had tumors that were discovered incidentally. Most stage I tumors (55%) were incidental. The 5-year progression-free survival rate was 86% for incidentally diagnosed tumors, versus 59% for symptomatic tumors (P = 0.007). On multivariate analysis, incidental detection of tumors was the strongest prognostic factor for progression. A sizable fraction of patients with early-stage pancreatic NETs are diagnosed incidentally during evaluations for other conditions or unrelated symptoms. This study highlights the necessity of developing guidelines for management of patients with incidentally discovered early-stage tumors.