The effect of race on the CYP3A-mediated metabolism of vincristine in pediatric patients with acute lymphoblastic leukemia.
OBJECTIVE
The purpose of this preliminary study was to compare racial background and CYP3A distribution in pediatric acute lymphoblastic leukemia patients as it relates to vincristine-related neurotoxicity.


METHODS
Patients with B-precursor acute lymphoblastic leukemia treated at Children's Hospital of Michigan were eligible to participate in this study. Determination of the CYP3A variant for each patient was done using Qiagen DNA Blood Mini Kit and polymerase chain reaction amplification. Patients were monitored during their leukemia treatment course for vincristine-related neurotoxicity.


RESULTS
Fifty-four patients were enrolled. Twenty-nine Caucasian patients (81%) and 13 African-American patients (77%) experienced neurotoxicity. CYP3A genotyping was done for 52 patients. Two African-American and two Caucasian patients were homozygous A/A for the CYP3A5*3 polymorphism. Three of these patients (75%) experienced grade 2 neuropathy. Two Caucasian patients and one African-American patient were heterozygous A/G. Two of these patients (66.7%) experienced grade 2 or 3 neuropathy. Thirty-five patients (67.3%) were homozygous for the mutant inactive G/G allele for CYP3A5*3, eight African-American and 27 Caucasian patients. Of these, six of the African-American patients (75%) and 22 of the Caucasian patients (81.5%) experienced neuropathy.


CONCLUSION
The CYP3A5*3 genotype causes very low expression of the CYP3A5 protein and hence decreased vincristine metabolism. In this study, patients who expressed CYP3A5*3 had an increased incidence of vincristine-related neurotoxicity. Overall, a greater percentage of Caucasian patients had documented incidences of neurotoxicity. A larger sample size and more detailed gene analysis are needed for future studies.