| Breast Cancer is found to be one of the leading | | | | Metabolizers who have zero enzyme levels to |
| causes of death among Hispanic women and various | | | | Ultra-rapid Metabolizers who have very high levels of |
| reports reveal that breast cancers are more | | | | the enzyme in the body. |
| aggressive in the Hispanic population. The study of | | | | Recent research shows that 5-10% of Hispanic |
| the role of genes and its effect on the activity of | | | | women are Poor Metabolizers. They are |
| drugs began when two distinct reactions were | | | | characterized by slower metabolism of the drug, due |
| observed on administration of a probe drug within | | | | to the absence of adequate quantities of the |
| the Hispanic group. While some people were able to | | | | enzyme. This might result in the build-up of |
| metabolize the probe drug, some people developed | | | | Tamoxifen as the body lacks an efficient mechanism |
| indications of not being able to metabolize the drug | | | | to eliminate the drug. Overall the slower metabolism |
| at all. This began the study of the prominent role | | | | of Poor Metabolizers may have a cascade effect |
| that genes play in drug metabolism. | | | | when multiple concomitant medications that are |
| CYP2D6 is a group of liver enzymes which have been | | | | metabolized by the CYP2D6 enzyme are |
| found to metabolize or break down 25% of all | | | | administered, increasing the potential for Adverse |
| clinically available medications. The CYP2D6 gene | | | | Drug Reactions. Poor Metabolizers may thus be |
| located on Chromosome 22 is responsible for the | | | | recommended to switch to an alternate method of |
| production of this enzyme in our body. A wide | | | | treatment as they lack the ability to convert |
| spectrum of drugs employed in the treatment of | | | | Tamoxifen into its active form, Endoxifen. They have |
| cancer are metabolized by this enzyme. The most | | | | been shown to have about three-fold risk of relapse |
| relevant medication for breast cancer is Tamoxifen | | | | than normal metabolizers. |
| and has been used for many years as an endocrine | | | | Ultra-rapid Metabolizers constitute another 5% of the |
| treatment for hormone-positive breast cancer with | | | | Hispanic population. They are characterized by higher |
| indications in the metastatic, adjuvant and preventive | | | | than normal conversion of Tamoxifen to its active |
| settings. The lower level of toxicity in Tamoxifen | | | | form, Endoxifen which results in high therapeutic |
| treatments when compared to chemotherapy helps | | | | effect of the drug. Although this population can |
| patients maintain quality of life and delay the use of | | | | experience the same benefit from a lower than |
| cytotoxic treatments (causing destruction of cells) | | | | standard dose of the drug, they face the possibility |
| for as long as possible. | | | | of serious side effects. |
| Tamoxifen is metabolized by the enzyme CYP2D6 | | | | Genetic testing has been recently recommended by |
| and it is converted into its active form called | | | | the FDA resulting in a label change for Tamoxifen |
| Endoxifen which then acts on the body. However the | | | | which plays an important role in preventing the |
| CYP2D6 gene exhibits variability across population and | | | | recurrence of breast cancer. Accredited DNA testing |
| among various ethnic groups. This results in variations | | | | laboratories like Genelex offer tests on receipt of a |
| in the levels of CYP2D6 enzyme in the body which | | | | physician prescription and delivers secure customized |
| leads to the difference in a person's ability to react | | | | reports on the effect of your genes on the drugs. |
| to the drug, Tamoxifen. Variability ranges from Poor | | | | |