KIT mutations and dose selection for imatinib in patients with advanced gastrointestinal stromal tumours

Eur J Cancer. 2006 May;42(8):1093-103. doi: 10.1016/j.ejca.2006.01.030. Epub 2006 Apr 18.

Abstract

A recent randomized EORTC phase III trial, comparing two doses of imatinib in patients with advanced gastrointestinal stromal tumours (GISTs), reported dose dependency for progression-free survival. The current analysis of that study aimed to assess if tumour mutational status correlates with clinical response to imatinib. Pre-treatment samples of GISTs from 377 patients enrolled in phase III study were analyzed for mutations of KIT or PDGFRA by combination of D-HPLC and direct sequencing of tumour genomic DNA. Mutation types were correlated with patients' survival data. The presence of exon 9-activating mutations in KIT was the strongest adverse prognostic factor for response to imatinib, increasing the relative risk of progression by 171% (P<0.0001) and the relative risk of death by 190% (P<0.0001) when compared with KIT exon 11 mutants. Similarly, the relative risk of progression was increased by 108% (P<0.0001) and the relative risk of death by 76% (P=0.028) in patients without detectable KIT or PDGFRA mutations. In patients whose tumours expressed an exon 9 KIT oncoprotein, treatment with the high-dose regimen resulted in a significantly superior progression-free survival (P=0.0013), with a reduction of the relative risk of 61%. We conclude that tumour genotype is of major prognostic significance for progression-free survival and overall survival in patients treated with imatinib for advanced GISTs. Our findings suggest the need for differential treatment of patients with GISTs, with KIT exon 9 mutant patients benefiting the most from the 800 mg daily dose of the drug.

Publication types

  • Clinical Trial, Phase III
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Antineoplastic Agents / therapeutic use*
  • Benzamides
  • Disease-Free Survival
  • Exons
  • Female
  • Gastrointestinal Stromal Tumors / drug therapy*
  • Gastrointestinal Stromal Tumors / genetics
  • Genotype
  • Humans
  • Imatinib Mesylate
  • Male
  • Middle Aged
  • Mutation / genetics*
  • Piperazines / therapeutic use*
  • Prognosis
  • Proto-Oncogene Proteins c-kit / genetics*
  • Pyrimidines / therapeutic use*
  • Retrospective Studies

Substances

  • Antineoplastic Agents
  • Benzamides
  • Piperazines
  • Pyrimidines
  • Imatinib Mesylate
  • Proto-Oncogene Proteins c-kit