When you first receive a diagnosis of breast cancer, your doctor will test your cancer cells to determine their hormone receptor status.
The two main hormone receptors that may be expressed on breast cancer cells are estrogen receptors (ER) and progesterone receptors (PR).The androgen receptor (AR) may also be involved, though its role in breast cancer is a bit more complex.
What are hormone receptors?
Hormone receptors are proteins found on the outside of cells that, when bound to their respective hormone, tell the cells to grow. Healthy breast cells contain hormone receptors, using them to regulate normal breast development and function.
In some patients with breast cancer, however, cancer cells learn how to take advantage of these receptors, using them to fuel uncontrolled cell growth.
Hormone receptor status in breast cancer
Breast cancer is typically classified as hormone receptor (HR)-positive or HR-negative. Individuals who have HR-positive breast cancer may express receptors for only estrogen, only progesterone, or both. To be classified as HR-positive, at least 1% of the tested cells in a breast cancer tumor must contain hormone receptors.
Learn more about the types of breast cancer
Approximately 70% to 80% of all breast cancers are HR-positive. The vast majority of HR-positive breast cancers are ER-positive. In fact, it’s rare to find a patient who is ER-negative and PR-positive.
How does hormone receptor status affect prognosis?
HR status is a major, but not the only, factor in determining breast cancer outcomes. In general, though, patients who are HR-positive tend to have better prognoses. This is in part because many therapies exist that can directly target these receptors, including:
- Selective estrogen receptor modulators: These are drugs that prevent estrogen from binding to estrogen receptors on cancer cells.
- Selective estrogen receptor degraders: These therapies break down estrogen receptors on cancer cells.
- Aromatase inhibitors: This is a class of drug that blocks an enzyme that the body uses to make estrogen.
- Luteinizing hormone-releasing hormone agonists: These drugs tell the brain to stop producing the signal that directs the ovaries to produce estrogen.
Patients who are HR-negative are not amenable to these types of drugs because their cancer cells do not respond to hormone signals.
HR-positive breast cancer typically grows slower than HR-negative breast cancer, improving short-term outcomes. While recurrence in HR-negative individuals is more likely to occur within a few years of treatment, recurrence of HR-positive tumors may occur many years later.
Keep in mind that HR status is not the only determinant of prognosis or relapse. Your cancer stage at diagnosis, age and race are just a few other factors that may influence prognosis.
The role of androgen receptors in breast cancer
Androgen receptors play a complex role in the development of breast cancer that still isn’t fully understood. Though estimates vary, around 70% to 85% of all breast cancers are AR-positive. AR-positivity may be linked with both better and poorer prognosis, depending on AR expression level, disease stage and disease subtype.
Research is still ongoing to determine whether targeting the androgen receptor may be a viable treatment option for patients with breast cancer, especially those who are HR-negative.