Breast Cancer Research and Treatment

, Volume 101, Issue 1, pp 113–121

The impact of cytochrome P450 2D6 metabolism in women receiving adjuvant tamoxifen

  • Matthew P. Goetz
  • Stacey K. Knox
  • Vera J. Suman
  • James M. Rae
  • Stephanie L. Safgren
  • Matthew M. Ames
  • Daniel W. Visscher
  • Carol Reynolds
  • Fergus J. Couch
  • Wilma L. Lingle
  • Richard M. Weinshilboum
  • Emily G. Barr Fritcher
  • Andrea M. Nibbe
  • Zeruesenay Desta
  • Anne Nguyen
  • David A. Flockhart
  • Edith A. Perez
  • James N. Ingle
Epidemiology

DOI: 10.1007/s10549-006-9428-0

Cite this article as:
Goetz, M.P., Knox, S.K., Suman, V.J. et al. Breast Cancer Res Treat (2007) 101: 113. doi:10.1007/s10549-006-9428-0

Abstract

Background

Tamoxifen is biotransformed to the potent anti-estrogen, endoxifen, by the cytochrome P450 (CYP) 2D6 enzyme. CYP2D6 genetic variation and inhibitors of the enzyme markedly reduce endoxifen plasma concentrations in tamoxifen-treated patients. Using a North Central Cancer Treatment Group adjuvant tamoxifen trial, we performed a comprehensive evaluation of CYP2D6 metabolism by assessing the combined effect of genetic variation and inhibition of the enzyme system on breast cancer recurrence and death.

Methods

Medical records were reviewed at each randomizing site to determine whether CYP2D6 inhibitors were co-prescribed with tamoxifen. Extensive metabolizers were defined as patients without a *4 allele (i.e., wt/wt) who were not co-prescribed a CYP2D6 inhibitor. Patients with decreased CYP2D6 metabolism were classified as intermediate or poor metabolizers (PM) based on the presence of one or two CYP2D6*4 alleles or the co-administration of a moderate or potent CYP2D6 inhibitor. The association between CYP2D6 metabolism and clinical outcome was assessed using Cox modeling.

Results

Medication history was available in 225/256 eligible patients and CYP2D6*4 genotype in 190 patients. Thirteen patients (6%) were co-prescribed a CYP2D6 inhibitor [potent (n = 3), moderate (n = 10)], resulting in the following CYP2D6 metabolism: extensive (n = 115) and decreased (n = 65). In the multivariate analysis, patients with decreased metabolism had significantly shorter time to recurrence (p = 0.034; adj HR = 1.91; 95% CI 1.05–3.45) and worse relapse-free survival (RFS) (p = 0.017; adj HR = 1.74; 1.10–2.74); relative to patients with extensive metabolism. Cox’ modeling demonstrated that compared to extensive metabolizers, PM had the most significant risk of breast cancer relapse (HR 3.12, p = 0.007).

Conclusion

CYP2D6 metabolism, as measured by genetic variation and enzyme inhibition, is an independent predictor of breast cancer outcome in post-menopausal women receiving tamoxifen for early breast cancer. Determination of CYP2D6 genotype may be of value in selecting adjuvant hormonal therapy and it appears CYP2D6 inhibitors should be avoided in tamoxifen-treated women.

Keywords

Tamoxifen Cytochrome P450 2D6 Pharmacogenetics Breast cancer 

Supplementary material

10549_2006_9428_MOESM1_ESM.pdf (208 kb)
Supplementary material

Copyright information

© Springer Science+Business Media, LLC 2006

Authors and Affiliations

  • Matthew P. Goetz
    • 1
  • Stacey K. Knox
    • 1
  • Vera J. Suman
    • 2
  • James M. Rae
    • 5
  • Stephanie L. Safgren
    • 1
  • Matthew M. Ames
    • 1
    • 4
  • Daniel W. Visscher
    • 3
  • Carol Reynolds
    • 3
  • Fergus J. Couch
    • 3
  • Wilma L. Lingle
    • 3
  • Richard M. Weinshilboum
    • 4
  • Emily G. Barr Fritcher
    • 3
  • Andrea M. Nibbe
    • 2
  • Zeruesenay Desta
    • 6
  • Anne Nguyen
    • 6
  • David A. Flockhart
    • 6
  • Edith A. Perez
    • 7
  • James N. Ingle
    • 1
  1. 1.Department of OncologyMayo Clinic College of MedicineRochesterUSA
  2. 2.Department of BiostatisticsMayo Clinic College of MedicineRochesterUSA
  3. 3.Department of Laboratory Medicine and PathologyMayo Clinic College of MedicineRochesterUSA
  4. 4.Department of Molecular Pharmacology and Experimental TherapeuticsMayo Clinic College of MedicineRochesterUSA
  5. 5.Division of Hematology/Oncology, Department of MedicineUniversity of Michigan School of MedicineAnn ArborUSA
  6. 6.Division of Clinical Pharmacology, Department of MedicineIndiana UniversityBloomingtonUSA
  7. 7.Division of Hematology and Oncology, Department of MedicineMayo ClinicJacksonvilleUSA

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