Variable | Base case | Range for sensitivity analysis | Distribution for probabilistic sensitivity analysis | Reference |
---|---|---|---|---|

Probabilities | ||||

Annual probability of recurrence post abdominoperineal resection | 0.0871 |
0.0435–0.130^{a}
| Beta | Rutkowski et al. [8] |

Annual conditional probability of local recurrence post abdominoperineal resection^{a}
| 0.135 |
0.0675–0.203^{a}
| Uniform | Rutkowski et al. [8] |

Annual probability of 1st progression in metastatic GIST | 0.370 |
0.296–0.444^{b}
| Beta | Blanke et al. [4] |

Annual probability of 2nd progression in metastatic GIST | 0.811 |
0.649–0.973^{b}
| Beta | Blanke et al. [4] |

Annual probability of 3rd progression in metastatic GIST | 0.708 |
0.566–0.850^{b}
| Beta | Demetri et al. [13] |

Annual probability of death in metastatic GIST post-regorafenib | 0.405 |
0.270–0.410^{b}
| Beta | Demetri et al. [14] |

Utilities | ||||

Recurrence-free health state post abdominoperineal resection | 0.830 | 0.650–1 | Beta | Miller et al. [7] |

Recurrence-free health state on continued imatinib until progression | 0.935 |
0.750–1^{b}
| Beta | Wilson et al. [17] |

GIST recurrence | 0.748 |
0.598–0.898^{b}
| Beta | Majer et al. [10] |

GIST 1st progression in metastatic disease | 0.712 | 0.685–0.739 | Beta | Chabot et al. [18] |

GIST 2nd progression in metastatic disease | 0.712 | 0.685–0.739 | Beta | Assumption |

GIST 3rd progression in metastatic disease | 0.712 | 0.685–0.739 | Beta | Assumption |

COSTS (SGD) | ||||

Annual cost of imatinib 400 mg once daily | 37 040 |
7 408–44 448^{c}
| Gamma | NCCS data |

Annual cost of sunitinib 50 mg once daily 4 weeks on, 2 weeks off | 64 063 |
51 250–76 876^{b}
| Gamma | NCCS data |

Annual cost of regorafenib 160 mg once daily 3 weeks on, 1 week off | 72 001 |
57 601–86 401^{b}
| Gamma | NCCS data |

Abdominoperineal resection | 38 000 |
30 400 –45 600^{b}
| Gamma | NCCS data |

Salvage surgery (following 1st local recurrence post abdominoperineal resection) | 38 000 |
30 400–45 600^{b}
| Gamma | NCCS data |

Annual cost of follow-up (consultation, blood tests, computer tomography scans every 3 months) | 3 000 |
2 400–3 600^{b}
| Gamma | NCCS data |