title: CYP2D6 polymorphisms influence the efficacy of adjuvant tamoxifen in Thai breast cancer patients.
abstract: OBJECTIVE
  We evaluated single nucleotide polymorphisms (SNPs) of CYP2D6 to identify those that influence the efficiency of tamoxifen in adjuvant treatment of breast cancer through a matched case-control study.
  
  
  METHODS
  Peripheral blood DNA was collected from 20 patients with disease recurrence during adjuvant tamoxifen treatment and from 19 patients who had completed 5 years of tamoxifen therapy without recurrence of breast cancer. CYP2D6*4 (1846G > A; rs3892097), CYP2D6*10 (100C > T, rs1065852), and CYP2D6*5 (deletion) were genotyped. The correlation between disease-free survival (DFS) and genotype and clinical outcome were assessed using Kaplan-Meier analysis and a log-rank test.
  
  
  RESULTS
  We found the allelic frequency of CYP2D6*10 during this study. Patients with the CYP2D6*10 homozygous variant T/T genotype had a significantly shorter median of DFS than those with C/T (P = 0.036), but DFS was not significantly different from that of patients with the C/C genotype (P = 0.316). One patient who was a carrier both of CYP2D6 G/A (1846G > A) and T/T (100C > T) had DFS of 22.7 months.
  
  
  CONCLUSIONS
  This study demonstrated that CYP2D6*10/*10 was significantly associated with shorter DFS in Thai breast cancer patients receiving tamoxifen. This was a pilot study investigating the correlation of CYP2D6 polymorphisms and their influence on clinical outcomes in Thai estrogen receptor-positive breast cancer patients.
authors.affiliation: Division of Medical Oncology, Department of Medicine.
authors.forename: Ekaphop
authors.initials: E
authors.lastname: Sirachainan
authors.forename: Sureerat
authors.initials: S
authors.lastname: Jaruhathai
authors.forename: Narumol
authors.initials: N
authors.lastname: Trachu
authors.forename: Ravat
authors.initials: R
authors.lastname: Panvichian
authors.forename: Thitiya
authors.initials: T
authors.lastname: Sirisinha
authors.forename: Touch
authors.initials: T
authors.lastname: Ativitavas
authors.forename: Vorachai
authors.initials: V
authors.lastname: Ratanatharathorn
authors.forename: Montri
authors.initials: M
authors.lastname: Chamnanphon
authors.forename: Chonlaphat
authors.initials: C
authors.lastname: Sukasem