Figure 1.
Model to assess GIST patient prevalence in the UK at different treatment stages. GIST = gastrointestinal stromal tumour; TTT = time to transition; UK = United Kingdom. The model parameters are given in Table 1. Z1 refers to the total UK population and is fixed in all calculations at 62,262,000. Z2 is the number of patients with non-metastatic GIST who have been resected and are currently recurrence free. Z3 is the number of patients with non-resectable metastatic GIST and who are currently progression free while receiving treatment with imatinib. Similarly, Z4 and Z5 are the numbers of patients who are progression-free while receiving sunitinib and a third-line treatment, respectively. γ2 is the annual rate of relapse which is estimated from the duration of relapse-free survival in this state. γ3 is the annual rate of failure calculated from the duration of PFS and TTP on imatinib. γ4 is the annual rate of failure calculated from the duration of PFS and TTP on sunitinib. γ5 is the annual probability of failure calculated from the duration of OS on a range of investigational third-line treatments or best supportive care. Γ = incidence of newly diagnosed GIST. p = proportion.