Description Module
The Description Module contains narrative descriptions of the clinical trial, including a brief summary and detailed description. These descriptions provide important information about the study's purpose, methodology, and key details in language accessible to both researchers and the general public.
Description Module path is as follows:
Study -> Protocol Section -> Description Module
Description Module
Ignite Creation Date:
2025-12-24 @ 4:07 PM
Ignite Modification Date:
2025-12-24 @ 4:07 PM
NCT ID:
NCT00873366
Brief Summary:
RATIONALE: A breath test that measures enzymes may be effective in identifying women in whom tamoxifen may not be effective.
PURPOSE: This clinical trial is studying a breath test to see how well it works in women receiving tamoxifen for the prevention or treatment of breast cancer.
Detailed Description:
OBJECTIVES:
* To assess the operating characteristics of the ¹³C-dextromethorphan (\^13 C-DM) breath test in identifying women with breast cancer (or at high risk) who are CYP2D6-genotypic poor metabolizers.
* To examine the correlation between CYP2D6 enzyme activity (as measured by the breath test) and plasma endoxifen (and 4-hydroxyTAM) levels in patients who carry one or more CYP2D6 functional alleles.
* To examine the change in CYP2D6 enzyme activity (as measured by the ¹³C-DM breath test), in patients who start a CYP2D6 inhibitor while taking tamoxifen.
* To determine whether CYP2D6 enzyme activity (as measured by the breath test) changes over time (either as a consequence of drug-induced inhibition or other).
* To measure genetic variation in additional genes that are later identified to affect the metabolism, uptake, or distribution of tamoxifen (e.g., SULT1A1, UGT).
OUTLINE: Patients receive tamoxifen citrate for 6 months. \^13C-dextromethorphan breath tests are conducted at baseline and periodically during the 6 months.
13C-dextromethorphan breath test: Patients receive oral Alka-Seltzer® Gold (ASG; citric acid, potassium bicarbonate, and sodium bicarbonate) in water, then, 15 minutes later, another ASG dose and oral ¹³C-dextromethorphan. Patients breathe into a bag 1-2 times, and the is bag sealed. ¹³CO\_2 levels in the bags are measured.
Blood samples are collected at baseline and periodically for pharmacogenetic and pharmacokinetic studies by reverse phase HPLC with fluorescence detection.
After completion of study therapy, patients are followed annually for 5 years.
Study:
NCT00873366
Study Brief:
Protocol Section:
NCT00873366