Tamoxifen Dose Adjustment on Indonesian Female ER+ Breast Cancer Patients Based on CYP2D6 Genotype and Endoxifen Levels

Tamoxifen Dose Adjustment on ER+ Breast Cancer Patients Based on Genomic and Metabolite Concentrations Analysis

Status

Completed

Phases

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT04312347

Enrollment

151

Registered

2020-03-18

Start date

2019-09-06

Completion date

2021-06-30

Last updated

2021-08-05

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

ER+ Breast Cancer

Keywords

breast cancer, tamoxifen, CYP2D6, endoxifen

Brief summary

The objectives of this study is to perform CYP2D6 genotyping and metabolite concentrations analysis on ER+ breast cancer patients who are taking tamoxifen and give dose recommendations based on the CYP2D6 genotypes and endoxifen levels.

Interventions

DRUGTamoxifen dose adjustment

Patients with low endoxifen level and poor/intermediate metabolizer CYP2D6 phenotype will receive tamoxifen dose escalation into 40 mg/day.

Study design

Allocation

Intervention model

SINGLE_GROUP

Primary purpose

TREATMENT

Masking

NONE

Eligibility

Sex/Gender

FEMALE

Age

18 Years to No maximum

Healthy volunteers

Inclusion criteria

* Diagnosed with ER+ breast cancer * Have taken tamoxifen daily for at least 2 months

Exclusion criteria

* Have not taken tamoxifen daily for at least 2 months

Design outcomes

Primary

Measure	Time frame
Effects of genotype and phenotype of CYP2D6 on plasma and serum concentration of tamoxifen and its metabolites	8 weeks after initial tamoxifen intake
Effects of dose recommendation of tamoxifen based on CYP2D6 genotyping results on endoxifen levels	8 weeks after dose recommendation
Frequencies of CYP2D6 alleles in female Indonesian population	Baseline, pre-intervention

Countries

Indonesia

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Feb 4, 2026