If you or a loved one has been diagnosed with breast cancer, your doctor will test your hormone receptor (HR) status. But what does that mean, why does it matter and how can it affect your treatment decisions?
Seventy-80% of breast cancer cases are driven by the body’s natural hormones, estrogen and progesterone, which can fuel cancer growth. When a tumor is hormone receptor-positive (HR-positive), it responds to treatments that block the activity or the production of these hormones. However, not all HR-positive cancers are the same. Knowing the key biomarkers of your cancer, including whether your breast cancer is HR-positive, helps doctors guide your treatment plan, and this status helps determine which therapies might be most effective in preventing the cancer from growing. Let’s break down what this means, how it is determined and how treatment options differ.
What is hormone receptor-positive breast cancer?
Hormone receptor-positive breast cancer means that the cancer cells have receptors, or tiny proteins on their surface, that respond to estrogen and progesterone in our bodies. When estrogen and/or progesterone attach to these receptors, they cause the cancer cells to divide and the tumor to grow.
Some cancers are positive for both estrogen (ER) and progesterone receptors (PR), while others may be only ER+ and, in very rare cases, only PR+. There’s also triple-positive breast cancer, which is ER+, PR+ and HER2-positive, meaning it also expresses the human epidermal growth factor 2 protein (HER2). Each of these may respond differently to treatments.
Determining hormone receptor status
Your HR status is determined through biomarker testing on a tumor sample, typically during a biopsy or surgery. The test uses a tool called immunohistochemistry (IHC), which measures how many hormone receptors are present on the cancer cells. Results are reported as a percentage — higher percentages mean the tumor is more hormone-responsive.
Did you know if breast cancer returns or spreads (metastasizes), your HR status can change? For example, if the first tumor was treated with hormone therapies, a cancer that has returned may become resistant to that therapy. In other cases, a tumor may undergo changes or mutations to gain hormone receptor presence that it didn’t have before. That’s why doctors may recommend retesting the cancer’s biomarkers if it comes back or progresses.
Why your HR status matters
Your hormone receptor status affects almost every part of your treatment plan. HR-positive breast cancers tend to grow more slowly than HR-negative ones and often have more treatment options available.
- HR-positive, HER2-negative cancers are the most common type and often respond well to hormone therapy.
- HR-positive, HER2-positive cancers may need a combination of hormone therapy and HER2-targeted therapies.
- PR status may influence treatment decisions but is usually considered alongside ER status, as nearly all ER+ cancers are also PR+.
Treatment choices are based mainly on ER status. Depending on your HR status, for example, if you test ER+/PR-, your doctor may choose stronger or longer treatment approaches such as adding CDK4/6 inhibitors or extending hormone therapy beyond five years to ensure your treatment is tailored to your unique cancer.
Understanding these differences helps make sure you receive the best treatment for your diagnosis.
Targeted treatments for HR-positive breast cancer
Treatment for HR-positive breast cancer is tailored to block the cancer’s ability to use hormones for growth. The main approaches include:
- Hormone therapy: Medications that either block estrogen receptors or lower estrogen levels. These are often taken for five to ten years to reduce the risk of recurrence. Sticking to the prescribed hormone therapy by your doctor is crucial as studies show that when many doses are skipped or the hormone treatment is stopped early, there is a higher chance of cancer returning. Since the ovaries produce higher levels of estrogen during the menstrual cycle, some drug options depend on whether or not you are postmenopausal. There are three types of hormone therapies that work in different ways, including:
- Selective estrogen receptor modulators (SERMs). SERMs like tamoxifen block estrogen from activating the estrogen receptor.
- Aromatase inhibitors (AIs). Aromatase inhibitors like anastrozole, exemestane and letrozole stop the production of estrogen.
- Selective estrogen receptor degraders (SERDs). SERDs like fulvestrant and elacestrant get rid of the estrogen receptor altogether.
- Targeted therapies: Certain drugs work alongside hormone therapy to slow cancer growth, especially in advanced cases. These may include inhibitors that target specific proteins involved in cell division, like CDK4/6, mTOR or PI3K inhibitors.
Most individuals will also have a lumpectomy or mastectomy, often followed by radiation therapy to get rid of any remaining cancer cells. Your doctor will help determine the best combination of treatments based on your specific diagnosis and preferences.
Final considerations
HR-positive breast cancer often has more treatment options and a slower-growing rate compared to HR-negative types. Hormone-receptor negative breast cancers are not treated with hormone therapies because they do not have hormone receptors. Many individuals diagnosed with early-stage HR-positive breast cancer respond well to therapy and remain cancer-free after treatment. However, HR-positive cancers can sometimes recur years later, making long-term monitoring an important part of care.
Understanding the differences in hormone receptor status can empower you to make informed decisions about your care with your doctor.
Downloadable Resources:
Hormone Receptor-Positive Breast Cancer
Hormone Therapy for Breast Cancer Treatment
Questions to Ask Your Doctor – Hormone Therapy
Hormone Receptor Negative Breast Cancer
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