Table 1.
Transition probabilities, utilities and costs
| Variable | Base case | Range for sensitivity analysis | Distribution for probabilistic sensitivity analysis | Reference |
|---|---|---|---|---|
| Probabilities | ||||
| Annual probability of recurrence post abdominoperineal resection | 0.0871 | 0.0435–0.130a | Beta | Rutkowski et al. [8] |
| Annual conditional probability of local recurrence post abdominoperineal resectiona | 0.135 | 0.0675–0.203a | Uniform | Rutkowski et al. [8] |
| Annual probability of 1st progression in metastatic GIST | 0.370 | 0.296–0.444b | Beta | Blanke et al. [4] |
| Annual probability of 2nd progression in metastatic GIST | 0.811 | 0.649–0.973b | Beta | Blanke et al. [4] |
| Annual probability of 3rd progression in metastatic GIST | 0.708 | 0.566–0.850b | Beta | Demetri et al. [13] |
| Annual probability of death in metastatic GIST post-regorafenib | 0.405 | 0.270–0.410b | 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 | 0.750–1b | Beta | Wilson et al. [17] |
| GIST recurrence | 0.748 | 0.598–0.898b | 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 448c | Gamma | NCCS data |
| Annual cost of sunitinib 50 mg once daily 4 weeks on, 2 weeks off | 64 063 | 51 250–76 876b | Gamma | NCCS data |
| Annual cost of regorafenib 160 mg once daily 3 weeks on, 1 week off | 72 001 | 57 601–86 401b | Gamma | NCCS data |
| Abdominoperineal resection | 38 000 | 30 400 –45 600b | Gamma | NCCS data |
| Salvage surgery (following 1st local recurrence post abdominoperineal resection) | 38 000 | 30 400–45 600b | Gamma | NCCS data |
| Annual cost of follow-up (consultation, blood tests, computer tomography scans every 3 months) | 3 000 | 2 400–3 600b | Gamma | NCCS data |
mg milligrams, GIST gastrointestinal stromal tumor, NCCS National Cancer Centre Singapore, SGD Singapore dollars
a ± 50% (wider intervals used in estimation due to paucity of systematic data for recurrences specifically in rectal GIST post neoadjuvant imatinib)
b ± 20%
c + 20% and −80% (lower bound for imatinib extended to −80% to account for possible significant decrease in imatinib cost with advent of generic imatinib)