Clinical trial · Observational
Genotyping and Phenotyping of CYP2D6 Breast Cancer Patients on Tamoxifen
Genotyping and Phenotyping of CYP2D6 as Predictor of Z-endoxifen Plasma Levels in Breast Cancer Patients on Tamoxifen Treatment
NCT03504631CI-TRIAL-00032639unknownClinicalTrials.gov clinicaltrialsProvenance
- Source
- ClinicalTrials.gov
- Retrieved
- Sep 8, 2026
- Layer
- normalized (units and labels harmonized; values unchanged)
- Run
- ING-CLINICALTRIALS-20260908-000001
Summary
Brief summary (as posted)
This study is an observational study to determine phenotype and genotype of CYP2D6 as predictors of z-endoxifen concentrations in plasma of outgoing patients treated with tamoxifen for at least 4 months
Conditions
Conditions (1)
Free-text conditions as registered, with the CancerIndex entity they were reconciled to and the match type.
| Condition (as posted) | Mapped entity | Match | Confidence |
|---|---|---|---|
| Breast Cancer Female | Breast Neoplasm | ONTOLOGY_EXACT | 0.90 |
Interventions
Interventions (1)
| Intervention | Type | Mapped drug | Match |
|---|---|---|---|
| No intervention | Other | — | UNRESOLVED |
Design
Arms and outcomes
Arms (1)
- label
- Breast cancer patients on tamoxifen
- description
- Patients currently on treatment with tamoxifen for at least 4 months.
- interventionNames
- Other: No intervention
Primary outcomes (1)
- measure
- Genotype and phenotype of CYP2D6
- timeFrame
- 4 months
- description
- Number of subjects with CYP2D6 genotype and phenotype who had steady state level
Secondary outcomes (1)
- measure
- Z-endoxifen
- timeFrame
- 4 months
- description
- Number of subjects with plasma levels of Z-endoxifen more than 5.9 ng/mL
Eligibility
Eligibility (as posted)
- Sex
- Female
Show eligibility criteria text
Inclusion Criteria: * Breast cancer patients on tamoxifen treatment for at least 4 months Exclusion Criteria: * Abnormalities in liver markers (AST \>2.5 x ULN)
References
Publications (11)
- BACKGROUNDMadlensky L, Natarajan L, Tchu S, Pu M, Mortimer J, Flatt SW, Nikoloff DM, Hillman G, Fontecha MR, Lawrence HJ, Parker BA, Wu AH, Pierce JP. Tamoxifen metabolite concentrations, CYP2D6 genotype, and breast cancer outcomes. Clin Pharmacol Ther. 2011 May;89(5):718-25. doi: 10.1038/clpt.2011.32. Epub 2011 Mar 23. PMID 21430657
- BACKGROUNDJager NG, Rosing H, Schellens JH, Linn SC, Beijnen JH. Tamoxifen dose and serum concentrations of tamoxifen and six of its metabolites in routine clinical outpatient care. Breast Cancer Res Treat. 2014 Feb;143(3):477-83. doi: 10.1007/s10549-013-2826-1. Epub 2014 Jan 5. PMID 24390246
- BACKGROUNDTamminga WJ, Wemer J, Oosterhuis B, Brakenhoff JP, Gerrits MG, de Zeeuw RA, de Leij LF, Jonkman JH. An optimized methodology for combined phenotyping and genotyping on CYP2D6 and CYP2C19. Eur J Clin Pharmacol. 2001 May;57(2):143-6. doi: 10.1007/s002280100273. PMID 11417446
- BACKGROUNDDesta Z, Ward BA, Soukhova NV, Flockhart DA. Comprehensive evaluation of tamoxifen sequential biotransformation by the human cytochrome P450 system in vitro: prominent roles for CYP3A and CYP2D6. J Pharmacol Exp Ther. 2004 Sep;310(3):1062-75. doi: 10.1124/jpet.104.065607. Epub 2004 May 24. PMID 15159443
- BACKGROUNDFotoohi AK, Karim H, Lafolie P, Pohanka A, Ostervall J, Hatschek T, Vitols S. Pronounced Interindividual But Not Intraindividual Variation in Tamoxifen and Metabolite Levels in Plasma During Adjuvant Treatment of Women With Early Breast Cancer. Ther Drug Monit. 2016 Apr;38(2):239-45. doi: 10.1097/FTD.0000000000000257. PMID 26485084
- BACKGROUNDHennig EE, Piatkowska M, Karczmarski J, Goryca K, Brewczynska E, Jazwiec R, Kluska A, Omiotek R, Paziewska A, Dadlez M, Ostrowski J. Limited predictive value of achieving beneficial plasma (Z)-endoxifen threshold level by CYP2D6 genotyping in tamoxifen-treated Polish women with breast cancer. BMC Cancer. 2015 Aug 1;15:570. doi: 10.1186/s12885-015-1575-4.