Abstract:
Background Activating mutations of KIT have been described to be the crucial molecular pathogenesis of gastrointestinal-stromal tumor (GIST). Individual KIT mutations show different prognosis and differential response to the treatment with imatinib. We investigated the prevalence and pattern of KIT mutation in GlST in Thai patients. Methods Thirty six GlST patients diagnosed and treated at the King Chulalongkorn Memo,-ial Hospital during 2002-2008 who had adequate archival parafin-embedded tumor tissue were identified. DNA was extracted from tumor tissue and then amplified by PCR with primers for KIT exon 11 and exon 9. All PCR products were subjected to direct sequencing. The associations between KIT mutation and tunior response to treatment, time to progression (TTP), and overall survival (0s) were analyzed. Results We successfully amplified 24 out of 36 tumor materials. Mutations of KIT exon 11 were detected in 15 out of 24 tumors (62.5%) and mutations of KIT exon 9 were demonstrated in 4 tumors (16.7%). Most of KIT exon 11 mutations were deletion (10/15:66.7%), complex mutation (3115: 20%) and substitutions (2115: 13.3%). Mutations of KIT exon 9 were all gene duplication (414: 100%). The median follow-up time was 22.5 months. There was a trend toward better treatment outcomes in advanced GlST with KIT exon 11 mutations than non-KIT exon 11 mutations. The objective response were 62.5% vs 37.5% (p=0.74), TTP were 33.1 months vs 21.6 months (p=0.08) and OS were 41.7 months vs 31.3 months (p=0.26) for KIT exon11 mutation vs non-KIT exon11 mutation respectively. Conclusion Our study shows similar prevalence of KIT mutations in Thai GlST patients consistent with the other previous reports. Mutation of exon 11 associates with better imatinib response, time to progression, and overall survival.