title: Prevalence of gastrointestinal stromal tumour (GIST) in the United Kingdom at different therapeutic lines: an epidemiologic model.
abstract: BACKGROUND
  The prevalence of patients with gastrointestinal stromal tumourgst (GIST) who fail currently available treatments imatinib and sunitinib (third-line treatment-eligible GIST) is unknown, but is expected to be below an ultra-orphan disease threshold of 2/100,000 population used in England and Wales. Our study was designed to estimate the prevalence and absolute number of UK patients with unresectable/metastatic GIST at first-, second- and eventually third-line treatment.
  
  
  METHODS
  Our open population model estimates the probability that the prevalence of UK third-line treatment-eligible GIST patients will remain under the ultra-orphan disease threshold. Model parameters for incidence, proportion of unresectable/metastatic disease and survival estimates for GIST patients were obtained from a targeted literature review and a UK cancer register. The robustness of the results was checked through differing scenarios taking extreme values of the input parameters.
  
  
  RESULTS
  The base-case scenario estimated a prevalence of third-line treatment-eligible GIST of 1/100,000 and a prevalence count of 598 with a 99.9% likelihood of being below the ultra-orphan disease threshold. The extreme scenarios, one-way and probabilistic sensitivity analyses and threshold analysis confirmed the robustness of these results.
  
  
  CONCLUSIONS
  The prevalence of third-line treatment-eligible GIST is very low and highly likely below the ultra-orphan disease threshold.
authors.forename: Justyna M
authors.initials: JM
authors.lastname: Starczewska Amelio
authors.affiliation: Health Economics and Epidemiology, Evidera, Metro Building, 6th floor, No,1 Butterwick, London W6 8DL, UK. javier.cid@evidera.com.
authors.forename: Javier
authors.initials: J
authors.lastname: Cid Ruzafa
authors.forename: Kamal
authors.initials: K
authors.lastname: Desai
authors.forename: Spiros
authors.initials: S
authors.lastname: Tzivelekis
authors.forename: Dominic
authors.initials: D
authors.lastname: Muston
authors.forename: Javaria Mona
authors.initials: JM
authors.lastname: Khalid
authors.forename: Philip
authors.initials: P
authors.lastname: Ashman
authors.forename: Andrew
authors.initials: A
authors.lastname: Maguire
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001549:Benzamides / Q000627:therapeutic use*; D046152:Gastrointestinal Stromal Tumors / Q000188:drug therapy* / Q000453:epidemiology* / Q000401:mortality / Q000556:secondary; D006801:Humans; D000068877:Imatinib Mesylate; D015994:Incidence; D007211:Indoles / Q000627:therapeutic use*; D015233:Models, Statistical; D010879:Piperazines / Q000627:therapeutic use*; D015995:Prevalence; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use*; D011743:Pyrimidines / Q000627:therapeutic use*; D011758:Pyrroles / Q000627:therapeutic use*; D035583:Rare Diseases / Q000188:drug therapy* / Q000453:epidemiology* / Q000401:mortality; D012042:Registries; D000077210:Sunitinib; D017211:Treatment Failure; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D007211:Indoles; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D011758:Pyrroles; D000068877:Imatinib Mesylate; D000077210:Sunitinib