CYP2D6 Genotypes and Breast Cancer Clinical Outcomes in the Indonesian Population

CYP2D6 Genotypes and Breast Cancer Clinical Outcomes in the Indonesian Population (Pengaruh Genotipe CYP2D6 Terhadap Efektivitas Penggunaan Tamoksifen Untuk Pasien Kanker Payudara ER+ Pada Populasi Indonesia)

Status

UNKNOWN

Phases

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT05501158

Enrollment

150

Registered

2022-08-15

Start date

2021-01-01

Completion date

2024-06-30

Last updated

2022-08-19

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

Conditions

Breast Cancer

Brief summary

The utilization of tamoxifen is considerably high in Indonesia, with about 170,000 tamoxifen prescriptions filed in 2015. It is metabolized by the enzyme CYP2D6, resulting in its active metabolite, endoxifen, which has been proven to be effective in the prevention and treatment of breast cancer. Studies showed the CYP2D6 gene has more than 100 variants; some of which are linked with reduced drug activity, while others do not have any pathological implications. The metabolizer profile of these variants is generally grouped into Ultra-rapid, Normal, Intermediate, and Poor Metabolizers (UM, NM, IM, and PM, respectively). In our previous study (NCT04312347), the investigators recruited 150 breast cancer patients who were taking adjusted dose of tamoxifen daily based on their CYP2D6 phenotype. Although the investigators have measured the endoxifen level of the patients with adjusted treatment, the clinical outcomes of the study are not yet conclusive.

Interventions

DRUGTamoxifen

Suggesting an increase in the dose of tamoxifen to those who have suboptimum level of endoxifen due to their genetic variations

Study design

Allocation

NON_RANDOMIZED

Intervention model

SINGLE_GROUP

Primary purpose

TREATMENT

Masking

NONE

Intervention model description

This is a prospective cohort study involving the breast cancer patients who participated in our previous study. Patients who are recommended to adjust their tamoxifen dosage to 40 mg and remain on tamoxifen 20 mg will be all followed up for 3 years to evaluate the clinical outcomes and medication side effects

Eligibility

Sex/Gender

FEMALE

Healthy volunteers

Inclusion criteria

1. female 2. diagnosed with ER+ breast cancer 3. have been genotyped and classified as PM and IM in the previous study 4. are recommended by doctor to take tamoxifen 40 mg according to their metabolizer profile 5. have finished the definitive therapy course (surgery, chemotherapy, or radiotherapy).

Exclusion criteria

1. have other primary cancer aside from breast cancer. 2. those with residual tumor cells/have experienced second primary breast tumor. 3. patients who are recommended by doctor to switch to aromatase inhibitors (AI)

Design outcomes

Primary

Measure	Time frame	Description
Overall Survival rate	3 year	The percentage of study participants who are still alive by the end of this study after being diagnosed with breast cancer
Progression Survival rate	3 year	The percentage of study participants who live with the disease but the disease does not get worse by the end of this study

Other

Measure	Time frame	Description
Long-term side effects of tamoxifen	3 year	Long-term side effects of tamoxifen, including heartburn, thromboembolic event, endometrial hyperplasia and uterine cancer, will also be monitored and documented using the Adverse Drug Reaction (ADR) reporting form provided by the Indonesian National Agency of Drug and Food Control.

Countries

Indonesia

Outcome results

None listed

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