TEST CODE: 008864

DIAGNOSTIC TEST FOR: TAMOXIFEN SENSITIVITY ASSAY

TURNAROUND TIME: 10–21 calendar days (14 days on average)

PREFERRED SPECIMEN: 3mL whole blood in a purple-top tube

ALTERNATE SPECIMENS: DNA or saliva/assisted saliva

Tamoxifen Sensitivity Assay

What is Tamoxifen? 

The growth of some breast cancers is stimulated by the female sex hormones estrogen and progesterone. There are two main types of hormone driven breast cancers: 

– Estrogen Receptors (ER+): These breast cancers use the hormone estrogen to grow. 

– Progesterone Receptors (PR+): These breast cancers use the hormone progesterone to grow. 

Tamoxifen is a nonsteroidal triphenylethylene based drug that is typically prescribed for women with Estrogen Receptor Positive (ER+) breast cancer. ER+ breast cancers have estrogen receptors in the breast cancer cells. Tamoxifen works by locking on to the estrogen receptors to block estrogen from attaching to them. The estrogen cannot then stimulate the cells to divide and grow.   Tamoxifen has been in clinical use for the treatment of breast cancer since the 1970’s and may reduce the risk of recurrence and death when given as adjuvant therapy for early stage disease. Tamoxifen has also been recommended for use in women who may be at high risk of developing breast cancer.  

Women who are at high risk because of a very strong family history may benefit from hormones such as tamoxifen, usually administered over five years.  Women over 35 years of age with moderate risk or women of any age with high risk of breast cancer, consider the use of medication such as tamoxifen, to reduce the risk of developing breast cancer.

Key factors associated with increased risk due to family history include: 

– multiple relatives affected by breast cancer or ovarian cancer on the same side of the family 

– younger age at cancer diagnosis in relatives (i.e. under 40 years) 

– relative with an identified mutation in a high-risk breast cancer gene, such as BRCA1or BRCA2 

– relatives affected with bilateral breast cancer 

– breast and ovarian cancer in the same relative 

– Ashkenazi Jewish ancestry. 

How could the Tamoxifen Sensitivity Assay benefit me? 

Hormone-based treatment, such as tamoxifen, has turned out to be one of the mainstream treatments in estrogen receptor positive breast cancer, and brought about a great improvement in disease-free survival (DFS) and overall survival (OS). However, adjuvant hormone therapy does not work as intended for a considerable amount of breast cancer patients and thus, identification of markers for better selection of endocrine treatment is needed.

Aromatase is an enzyme encoded by the CYP19A1 gene, that catalyses the final step of the conversion of androgens to estrogens. Estrogens play an important role in breast cancer development in estrogen receptor positive Breast Cancers. Approximately 60% of premenopausal and 75% of postmenopausal patients have estrogen positive carcinomas.   Given the critical role that CYP19A1 plays in the synthesis of estrogen, it is believed that genetic variants in the gene may be a useful marker in determining a patient’s likely response to hormone-based therapies such as Tamoxifen.  

The Tamoxifen Sensitivity Assay has been specifically designed for breast cancer patients, or women with an increased risk of breast cancer, and detects the CYP19A1 gene. The assay specifically looks for a single nucleotide polymorphism in the CYP19A1 gene – SNP rs4646 – to determine your genotype. There is growing evidence to suggest that based on your genotype, you may have an increased or decreased response to Tamoxifen treatment. For patients considering treatment with Tamoxifen, the Tamoxifen Sensitivity Assay can be used to determine your CYP19A1 genotype. This in turn can help you and your health care provider determine if Tamoxifen is suitable for you, and if adjustments to dosages are required.  

Ready to take control of your treatment plan?

Genomed aims to educate patients and their families on their cancer types and empower them with the knowledge to take control of their treatment plans. As each patient’s case is unique, there is no “one size fits all” when it comes to testing. We encourage you to contact Genomed, and we can work with you and your oncologist/specialist, to determine what tests would benefit you.