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GIST Support International - Mutations in GISTs
Predicted imatinib response and GIST characteristics based on the mutation of the primary tumor in the KIT or PDGFRA genes.
| Mutation | Frequency | Response to Imatinib * | Histological cell type | Anatomical Site |
| KIT gene | 80-85% | mostly spindle (long tapered shape) | any site | |
exon 9 | 10% | ~80% | small bowela | |
exon 11 | 60-70% | ~93% | any | |
exon 13 | 1% | ~100% b | any | |
exon 17 | 1% | ~75% | any | |
| PDGFRA gene | 5-10% | epithelioid (round shape) or mixed (spindle and epithelioid) | usually stomach | |
| exon 12 | 1% | some b | ||
| exon 14 | <1% | unknown | ||
| exon 18 | 6% | none | ||
| Wild Type adult GIST c (no KIT or PDGFRA mutation) | 10% | ~66% | any type | any site |
| * reported as "clinical benefit" including response or stable disease based on combined data from 3 clinical trials: B2222, EORTC phase I-II, EORTC Phase III. | ||||
| a Rarely gastric GIST can be exon 9. About a third of small intestinal GISTs are exon 9 mutant (remainder are exon 11). | ||||
| b Few data available. | ||||
c Pediatric/adolescent GISTs are usually wild-type but differ from adult wild-type GISTs in terms of histology and drug responsiveness. | ||||
