Tamoxifen PredictAR (CYP2D6)
Tamoxifen PredictAR determines a patients CYP2D6 genotype. This knowledge can help clinicians predict their patients response to tamoxifen.
Tamoxifen can be considered a prodrug that requires metabolism to elicit its pharmacological activity. Evidence now suggests that endoxifen, a secondary metabolite of tamoxifen, is most responsible for tamoxifen activity. In fact, endoxifen is 100 times more potent as an anti-oestrogen than tamoxifen itself.
CYP2D6 is the main enzyme that metabolises tamoxifen to endoxifen. A number of commonly occurring gene variants have been identified in the CYP2D6 gene that result in clinically important changes to CYP2D6 enzyme activity. Approximately 10% of the Australian population have gene variants in their CYP2D6 gene that results in little or no enzyme activity. These individuals are known as poor metabolisers. As such, poor metabolisers will not receive the full medical benefit of tamoxifen therapy since they have little capacity to metabolise tamoxifen to endoxifen. It has now been documented that CYP2D6 poor metabolisers, treated with tamoxifen, tend to have a shorter relapse-free time, worse relapse-free survival and significantly more recurrence of their disease.
References :
Jin Y, Desta Z, Stearns V., et al. CYP2D6 Genotype, Antidepressant Use, and Tamoxifen
Metabolism During Adjuvant Breast Cancer Treatment. J Natl Cancer Inst 2005; 97: 30-9.
Goetz M.P., Knox S.K., Suman V.J., et al. The impact of cytochrome P450 2D6
metabolism in women receiving adjuvant tamoxifen. Breast Cancer Res Treat 2007; 101:
113-121.
Borges S, Desta Z, Li L., et al. Quantitative effect of CYP2D6 genotype and inhibitors on
tamoxifen metabolism: Implication for optimisation of breast cancer treatment.
Clin Pharmacol Ther 2006; 80:61-74.
the Impact on Tamoxifen Therapy. J Pharmaceutical Sciences 2007; 96 (9): 2224-2231.
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| Medicare Rebate: | No |
| Specimen Type: | 4 mL whole blood (EDTA) |
| Test Frequency: | Daily (Mon-Fri) |
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