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GIST Support International - Mutations in GISTs
GIST Imagery

Predicted imatinib response and GIST characteristics based on the mutation of the primary tumor in the KIT or PDGFRA genes.

Mutation FrequencyResponse
to Imatinib
*
Histological
cell type
Anatomical
Site
KIT gene80-85%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 gene5-10%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%
more with stable disease than with
  partial response 

any typeany 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.



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