Interpreting the CYP2D6 results from the International Tamoxifen Pharmacogenetics Consortium

Clin Pharmacol Ther. 2014 Aug;96(2):144-6. doi: 10.1038/clpt.2014.100.


Meta-analysis of the entire analyzable cohort of 4,935 tamoxifen-treated breast cancer patients by the International Tamoxifen Pharmacogenetics Consortium (ITPC) (criterion 3) revealed no CYP2D6 effect on outcomes but strong heterogeneity across sites. However, a post hoc–defined subgroup (criterion 1: postmenopausal, estrogen receptor positive, receiving 20 mg/day tamoxifen for 5 years; n = 1,996) did find statistically significant effect of CYP2D6 on both invasive disease–free survival as well as breast cancer–free interval, with little site heterogeneity. How should we interpret these discrepant findings?

Publication types

  • Review

MeSH terms

  • Antineoplastic Agents, Hormonal / therapeutic use*
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / enzymology
  • Breast Neoplasms / genetics*
  • Congresses as Topic*
  • Cytochrome P-450 CYP2D6 / genetics*
  • Female
  • Humans
  • Pharmacogenetics / methods*
  • Tamoxifen / therapeutic use*


  • Antineoplastic Agents, Hormonal
  • Tamoxifen
  • Cytochrome P-450 CYP2D6