Hormone receptor-positive (HR-positive or HR+) breast cancer is a type of breast cancer that feeds on the presence of estrogen and progesterone hormones in the body to grow.
This type of breast cancer can be targeted with hormonal treatments to slow down the growth of the cancer cells or reduce the risk of recurrence.
The estrogen and progesterone hormones are naturally present in the body and play important roles in the female menstrual cycle and fertility.
However, for the majority of women with breast cancer, the abnormal cancer cells contain receptors that are activated in the presence of these hormones.
As a result, estrogen and progesterone can promote growth of some types of breast cancer cells, increasing their speed of replication and negatively impacting the health outcomes for the patient.
There are two types of hormone receptor positive breast cancer, according to the type of hormone that the receptor is associate with. These are:
- Estrogen receptor-positive (ER+) breast cancer: contains receptors for the estrogen hormone
- Progesterone receptor-positive (PR+) breast cancer: contain receptors for the progesterone hormone
When a woman is diagnosed with breast cancer, she will usually undergo tests to determine the type of breast cancer she has.
The pathology report will show the results of a hormone receptor assay, which portrays whether the breast cancer cells are hormone-receptor positive. This information is important because it will help to guide the best treatment decisions for the patient.
The result will categorize the breast cancer as one of the following:
- ER+ (approximately 75-80% of breast cancers are estrogen receptor-positive)
- ER+/PR+ (approximately 65% of breast cancers are both estrogen and progesterone receptor-positive)
- ER+/PR- (approximately 13% of breast cancers are estrogen receptor-positive and progesterone receptor-negative)
- ER-/PR+ (approximately 2% of breast cancers are estrogen receptor-negative and progesterone receptor-positive)
- ER-/PR- (approximately 20-25% of breast cancers are estrogen receptor-negative)
For women who have HR-positive cancer, hormonal therapy may be recommended as part of their treatment plan.
This may be prescribed as a stand-alone option, or as adjuvant treatment in combination with other therapies for breast cancer.
Hormonal therapy for breast cancer is distinct from hormonal replacement therapy (HRT) that is used in the management of menopause symptoms and it is important for patients to be aware of this.
HRT increases the levels of estrogen and progesterone in the body and can, therefore, have a negative effect on HR-positive breast cancer.
Instead, hormonal therapy for breast cancer has the opposite effect, which is to reduce the effect of hormones in the body. They may either lower the concentration or block the action of the hormones in the body.
There are several different types of hormonal therapy that may be indicated, depending on the characteristics of the patient and cancer. They may include:
- Selective estrogen-receptor response modulators (SERMs) such as tamoxifen or toremifene for pre- or post-menopausal women.
- Aromatase inhibitors such as anastrazole, exemestane, or letrozole for postmenopausal women, which work by blocking an enzyme that produces estrogen in the body.
- Estrogen-receptor downregulators (ERDs) such as fulvestrant, which block the effect of estrogen in the breast tissue.
- Luteinizing hormone-releasing hormone agents (LHRHs) such as goserelin, leuprolide, or triptorelin for pre-menopausal women, which inhibit the production of estrogen in the ovaries.
For some women, surgical removal of the ovaries with an oophorectomy may be the best option to lower the concentration of estrogen in the body and reduce the risk of breast cancer recurrence.