Predictive value of ABCB1 genotypes on dose adjustment of imatinib in patients with GIST (Gastro-Intestinal Stromal Tumour) and CML (Chronic Myeloid Leukaemia)

Interventions: The study will correlate the toxicity-adjusted dose of imatinib after 3 months of therapy with polymorphisms of drug elimination genes, particularly ABCB1 (MDR1). Patients will be asked to give a single blood sample for genotyping (at any time) and we will collect clinical data on dose and toxicity retrospectively from medical records.
Primary outcome(s): To determine whether ABCB1 genotype correlates with toxicity-adjusted dose of imatinib[At 3 months +/- 14 days]
Study Design: Purpose: Natural history;Duration: Cross-sectional;Selection: Defined population;Timing: Both