Written by : Dr.M.D.Mazumdar, MD
Hormone therapy, also known as 'endocrine therapy' or endocrine-based therapy", is a systemic therapy. A systemic therapy is a form of therapy (like chemotherapy) in which the drugs travel througout the body. It does not work on cancer cells alone.
Hormone or hormonal therapy interferes with the functions of hormones which may stimulate cancer growth. It blocks or removes hormones from the body to slow or stop the growth of cancer cells.
In the treatment of breast cancer, medicines prescribed during hormone therapy act against hormone-receptor-positive breast cancer (HER2 positive).
How do hormone therapy work?
Breast cells contain protein receptors called human epidermal growth factor receptor 2 (called 'HER2').
These receptors become activated when hormones bind to them. The activated receptors cause changes in the expression of specific genes, which can stimulate growth, division and repair of the breast cells.
Some cancer cells may make larger than normal amounts of HER2. This causes the cells to grow more quickly and be more likely to spread to other parts of the body.
Breast cancer cells which express HER2 is called hormone receptor positive breast cancer (HER2 positive).
HER2 Receptors in Normal and Breast Cancer cells
HER2 positive breast cancers are commonly seen in women with a gene called the ERBB2 gene. This gene can express larger amounts of HER2 which can then cause aggressive growth and faster spread of cancerous breast cells.
The HER2 receptors respond to circulating hormones, especially estrogen, in the blood. Hormone therapy is aimed at decreasing the estrogen level so that the receptors are not stimulated.
Both estrogen and progesterone hormone can attach to breast cancer cells which are receptor positive and affect their ability to multiply, but it is the estrogen receptors which are more sensitive .
About 75% of all breast cancers are hormone positive. Of these, about 60% are both estrogen receptor positive (ER+) and progesterone receptor positive (PR+). The rest 40% are only estrogen receptor positive (ER+). Breast tumors that contain both estrogen and/or progesterone receptors are called hormone receptor positive (HR positive).
The types of breast cancer that do not contain estrogen receptors are called estrogen receptor negative (ER negative). These cancers do not respond to hormone therapy. For these cancers, other treatment options like surgery or radiotherapy or chemotherapy are necessary. any
The purpose of hormone therapy is to either block the attachment between the receptors and the hormones or to decrease the level of circulating hormones, especially estrogen in the blood.
All breast cancers removed by surgery are biopsied and the tissue tested for both estrogen and progesterone receptors. Hormone therapy is beneficial in women with estrogen positive receptors but not very helpful in women with progesterone positive receptors.
HER2 positive breast cancers are more aggressive than negative cancers. They do not respond well to chemotherapy. There is also a greater risk of relapse and metastasis. So, an accurate assessment of the breast cancer is essential for a good prognosis.
When is Hormone Therapy for Breast cancer Advised?
Hormone Therapy for breast cancer is given in the following situations:
- Before breast surgery to shrink the tumor and make the surgery easier for both the patient as well as for the surgeon. This is known as neo-adjuvent therapy.
- As a preventive in women with very high risk for breast cancer, especially those women with a strong family history of breast cancer or those in whom breast cancer genes like BRIC has been identified..
- Together with lumpectomy which spares a part of the breast.
- Together with chemotherapy or radiotherapy.
- In recurrent or metastatic breast cancer.
Aim of Hormone Therapy
The aim of hormone therapy is to prevent stimulation of breast cancer cells by estrogen and progesterone - mainly estrogen. So, the drugs act on the cancer in two ways:
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