ArticleJournal of clinical pharmacology2025
From Genotype to Therapeutic Monitoring: Enhancing Tamoxifen Efficacy in Breast Cancer Treatment.
Article in Journal of clinical pharmacology, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 1 paper.
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
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Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
1 citing paper in PubMed.
- Tamoxifen Therapy Is Associated With Altered Intestinal P-Glycoprotein Activity In Vivo.Journal of clinical pharmacology · 2026Article
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Authors and funding
7 authors.
Funding
Abstract
Endoxifen is the most active metabolite of tamoxifen and plays a central role in its therapeutic efficacy. However, significant interindividual variability in endoxifen plasma concentrations, driven by both genetic and non-genetic factors, may result in subtherapeutic exposure for a substantial subset of patients. This study evaluated the influence of CYP2D6 phenotype and age on endoxifen steady-state concentrations and explored the clinical utility of therapeutic drug monitoring (TDM) to guide tamoxifen therapy. A total of 63 breast cancer patients receiving tamoxifen 20 mg daily for at least 3 months were enrolled. Patients were genotyped for CYP2D6 using TaqMan assays and classified as normal metabolizers (NMs, n = 49), intermediate metabolizers (IMs, n = 13), or ultrarapid metabolizers (UMs, n = 1). Plasma concentrations of tamoxifen and its metabolites were quantified by LC-MS/MS at steady state. Endoxifen levels were significantly lower in IMs (7.13 ng/mL; 95% CI: 3.38-15.08) compared to NMs (22.66 ng/mL; 95% CI: 18.57-27.66; P < .001). Subtherapeutic endoxifen concentrations (<6 ng/mL) were observed in 23.1% of IMs and 4.1% of NMs. These results support the combined use of CYP2D6 genotyping and TDM as the optimal strategy for personalizing tamoxifen therapy and minimizing the risk of subtherapeutic endoxifen exposure.
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