title: Population-level analysis of pancreatic neuroendocrine tumors 2 cm or less in size.
abstract: BACKGROUND
  There is a paucity of evidence regarding incidence and predictors of survival in pancreatic neuroendocrine tumors (PNETs)≤2 cm in size.
  
  
  METHODS
  Patients having undergone resection for nonfunctioning PNETs were selected from the SEER database (1988-2009) and an institutional pathology database (1996-2012). PNETs≤2 cm were compared with PNETs>2 cm. Data were analyzed with χ2 tests, ANOVA, the Kaplan-Meier method, log rank tests, and Cox proportional hazard, and binary logistic regression.
  
  
  RESULTS
  The incidence of PNETs≤2 cm in the United States has increased by 710.4% over the last 22 years. Rates of extrapancreatic extension, nodal metastasis, and distant metastasis in PNETs≤2 cm in the SEER database were 17.9, 27.3, and 9.1%, respectively. The rate of nodal metastasis in our institutional series was 5.7%. Disease-specific survival at 5, 10, and 15 years for PNETs≤2 cm was 91.5, 84.0, and 76.8%. Decreased disease-specific survival was not associated with nodal metastasis, but rather with high grade [moderately differentiated, hazard ratio (HR) 37.2, 95% confidence interval (CI) 2.7-518.8; poorly differentiated, HR 94.2, 95% CI 4.9-1,794.4; reference, well differentiated], and minority race (Asian, HR 30.2, 95% CI 3.1-291.7; Black, HR 60.1, 95% CI 2.1-1,027.9; reference, White).
  
  
  CONCLUSIONS
  Pancreatic neuroendocrine tumors≤2 cm are increasingly common, and the most significant predictors of disease-specific survival are grade and race. The SEER database excludes PNETs considered to be benign, and rates of extrapancreatic extension, nodal metastasis, and distant metastasis are overestimated. Small size, however, does not preclude malignant behavior.
authors.affiliation: Section of Surgical Oncology, Department of Surgery, Yale University School of Medicine, New Haven, CT, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Kuo
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Salem
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D002276:Carcinoid Tumor / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology; D018273:Carcinoma, Islet Cell / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology; D003237:Connecticut / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D018358:Neuroendocrine Tumors / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology; D011379:Prognosis; D012307:Risk Factors; D018426:SEER Program; D015996:Survival Rate; D055815:Young Adult