title: Peritoneal Metastases from Gastroenteropancreatic Neuroendocrine Tumors: Incidence, Risk Factors and Prognosis.
abstract: BACKGROUND
  Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare neoplasms and data on peritoneal metastases (PM) from these tumors are scarce.
  
  
  OBJECTIVE
  The aim of this study was to present population-based data on the incidence, risk factors, and survival of synchronous PM in GEP-NETs.
  
  
  METHODS
  Data from all patients diagnosed with a GEP-NET during 2007-2013 were collected from the Netherlands Cancer Registry. Age-standardized incidence rates were calculated and risk factors for developing PM were determined using multivariable logistic regression analysis. Survival was investigated using Kaplan-Meier and Cox regression analyses.
  
  
  RESULTS
  A total of 4114 patients were diagnosed with a GEP-NET. PM were diagnosed in 234 patients (19% of patients with metastasized disease, representing 6% of all GEP-NETs). The incidence of patients diagnosed with PM was 1.6:1,000,000 persons per year. Risk factors for developing PM were higher age (odds ratio [OR] 1.4, 95% CI 1.0-2.0) and primary tumor location in the small intestine (OR 3.5, 95% CI 2.1-5.7) or colon (OR 2.5, 95% CI 1.4-4.4). Small intestinal NETs with PM had the best survival, while appendiceal NETs with PM had the poorest survival (5-year survival rates of 67 and 7%, respectively). Multivariate analysis showed that survival in patients with PM was worse compared with patients without metastases; however, the presence of PM among all metastasized patients was not associated with worse survival.
  
  
  CONCLUSIONS
  This nationwide population-based study provides relevant insight into the incidence and risk factors of PM in GEP-NETs, and reveals detailed site-specific data on the presence of PM and survival data that may contribute to develop individualized treatment strategies in patients with these heterogeneous neoplasms.
authors.affiliation: Netherlands Comprehensive Cancer Organisation, Utrecht, The Netherlands. arianamadani@icloud.com.|Department of Public Health, Erasmus University Medical Center, Rotterdam, The Netherlands. arianamadani@icloud.com.|Department of Internal Medicine, Máxima Medical Center, Eindhoven, The Netherlands. arianamadani@icloud.com.
authors.forename: Ariana
authors.identifier: http://orcid.org/0000-0002-0398-9585
authors.initials: A
authors.lastname: Madani
authors.affiliation: Netherlands Comprehensive Cancer Organisation, Utrecht, The Netherlands.|Department of Surgery, Spaarne Gasthuis, Haarlem, The Netherlands.
authors.forename: Irene
authors.initials: I
authors.lastname: Thomassen
authors.affiliation: Netherlands Comprehensive Cancer Organisation, Utrecht, The Netherlands.
authors.forename: Yvette R B M
authors.initials: YRBM
authors.lastname: van Gestel
authors.affiliation: Department of Surgery, Academic Medical Center, Amsterdam, The Netherlands.|Department of Surgery, Flevoziekenhuis, Almere, The Netherlands.
authors.forename: Jarmila D W
authors.initials: JDW
authors.lastname: van der Bilt
authors.affiliation: Department of Internal Medicine, Máxima Medical Center, Eindhoven, The Netherlands.|Department of Internal Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.|CAPHRI School for Public Health and Primary Care, Maastricht University, Maastricht, The Netherlands.
authors.forename: Harm R
authors.initials: HR
authors.lastname: Haak
authors.affiliation: Department of Surgery, Catharina Cancer Center, Eindhoven, The Netherlands.
authors.forename: Ignace H J T
authors.initials: IHJT
authors.lastname: de Hingh
authors.affiliation: Netherlands Comprehensive Cancer Organisation, Utrecht, The Netherlands.|Department of Public Health, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Valery E P P
authors.initials: VEPP
authors.lastname: Lemmens
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007414:Intestinal Neoplasms / Q000453:epidemiology* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D018358:Neuroendocrine Tumors / Q000453:epidemiology* / Q000473:pathology / Q000556:secondary; D010190:Pancreatic Neoplasms / Q000453:epidemiology* / Q000473:pathology; D011379:Prognosis; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000453:epidemiology* / Q000473:pathology; D015996:Survival Rate