Background: KIT exon 11 mutations are observed in 60% of gastrointestinal stromal tumours (GIST). Exon 11 codes for residues Tyr568 and Tyr570, which play a major role in signal transduction and degradation of KIT. Our aim was to compare the outcome of patients with deletion of both Tyr568-570 (delTyr) and the most frequent deletion delWK557-558 (delWK).
Methods: Pathology and clinical characteristics of 68 patients with delTyr (n=26) or delWK (n=42) were reviewed and compared.
Results: GISTs with delTyr were more frequently extragastric than those with delWK (69 vs 26%, P<0.0005). After curative surgery, median relapse-free survival were 10.8 and 11.1 months for patients with delTyr (n=14) and delWK (n=29), respectively (P=0.92). All patients treated with imatinib for a non-resectable or metastatic GIST had an objective response (n=15) or a stable disease (n=21) as best response, regardless of mutation. Median progression-free survival with imatinib were 21.9 and 18.9 months for patients with GIST with delTyr (n=14) and delWK (n=22), respectively (P=0.43).
Conclusion: In this large retrospective series, the type of KIT exon 11 mutation was correlated with the origin of GIST, but not with prognosis or response to imatinib.