Tamoxifen (TAM) is a frequently used hormonal prodrug for patients with breast cancer that needs to be activated by cytochrome P450 2D6 (CYP2D6) into Zusammen-endoxifen (Z-END).
This study evaluated self-reported knowledge, practice, and attitudes toward commercially available cytochrome P450 2D6 (CYP2D6) pharmacogenomic testing for patients on tamoxifen for breast cancer (CYPT) among US oncologists while evidence for the use of the test was evolving.
The gene encoding the phase I enzyme cytochrome P4502D6 (CYP2D6) has been previously investigated for its potential predictive role in the efficacy of breast cancer treatments such as tamoxifen, but its role in breast cancer susceptibility is unclear.
To determine whether or not testing for cytochrome P450 2D6 (CYP2D6) polymorphisms in women with early hormone receptor positive breast cancer leads to improvement in outcomes, is useful for health decision-making and is a cost-effective use of health-care resources.
We explored whether breast cancer outcomes are associated with endoxifen and other metabolites of tamoxifen and examined potential correlates of endoxifen concentration levels in serum including cytochrome P450 2D6 (CYP2D6) metabolizer phenotype and body mass index (BMI).
Tamoxifen is extensively metabolized by cytochrome P450 enzymes, and recent in vivo studies have shown that women with genetically impaired cytochrome P450 2D6 have reduced production of endoxifen and a higher risk of breast cancer recurrence.