Tamoxifen

Tamoxifen, a widely used drug in the treatment and prevention of breast cancer, has a complex relationship with genetic information. Its effectiveness is significantly influenced by variations in an individual‘s genes, specifically those related to the CYP2D6 enzyme. This enzyme is responsible for metabolizing tamoxifen into its active form, endoxifen, which is crucial for its therapeutic effect.

Genetic influence 

Genetic variations in the CYP2D6 gene can affect the enzyme‘s activity, leading to differences in how individuals metabolize tamoxifen. Individuals with certain genetic variants may have reduced CYP2D6 activity, resulting in lower levels of endoxifen and potentially diminishing the drug‘s effectiveness. Studies have shown that women with reduced CYP2D6 activity may have a higher risk of breast cancer recurrence while taking tamoxifen. According to a 6-year follow-up study, the presence of two fully functional CYP2D6 alleles was associated with better clinical outcomes, while those with non-functional or reduced-function alleles had worse outcomes. Consequently, genetic testing for CYP2D6 variations is becoming increasingly important in personalizing tamoxifen therapy, ensuring that patients receive the most effective treatment based on their genetic profile.