Understanding Hormone-Positive Breast Cancer
By Sarah Friend, MD
When you hear the words hormone-positive breast cancer, it may feel overwhelming at first. However, by breaking it down step by step, you can better understand what this diagnosis means and how it will shape your treatment options.
What Does Hormone-Positive Mean?
Hormone-positive breast cancer refers to breast cancers that grow in response to hormones, specifically estrogen and/or progesterone. These cancers have special proteins, called receptors, on their surface. When hormones attach to these receptors, they can stimulate the cancer cells to grow.
Because of this, doctors often test every breast cancer for estrogen receptor (ER) and progesterone receptor (PR). If either is present, the cancer is called hormone-receptor-positive, or HR-positive. This distinction is very important because it directly influences your treatment plan.
How Do Doctors Measure Estrogen Receptors?
Doctors use a test called immunohistochemistry (IHC) to measure estrogen receptors. In this test, the pathologist examines the tumor under a microscope and reports the percentage of cells that stain positive for the estrogen receptor. The scale ranges from 0% to 100%.
- A tumor that is 100% ER-positive means that every cancer cell has estrogen receptors. These tumors are considered strongly estrogen-sensitive and are very likely to respond well to hormone blocking medications.
- A tumor that is only 1-2% ER-positive technically meets the definition of “ER positive,” since anything above 1% is classified as positive. However, these tumors are not considered strongly hormone-sensitive. They may respond less reliably to endocrine therapy, and doctors sometimes treat them more cautiously.
This nuance explains why two patients can both be labeled “ER-positive” but still have very different treatment responses and long-term expectations. Understanding your ER percentage can help you and your oncologist discuss the likely benefits of hormone therapy in your specific case.
Why Does This Matter?
Knowing that your breast cancer is hormone-positive opens up targeted treatment options. Instead of focusing only on chemotherapy or radiation, your care team may recommend hormone-blocking therapies. These treatments slow or stop the effect of estrogen or progesterone on the cancer cells, essentially “cutting off the fuel supply.”
As a result, hormone-positive breast cancers often respond very well to treatment. In fact, they are considered to have some of the most effective and longest-lasting therapy options available.
How Do Doctors Treat Hormone-Positive Breast Cancer?
Treatment usually combines different approaches. Each step is designed to both remove visible cancer and prevent it from coming back.
- Surgery and Radiation – most people start with surgery to remove the tumor followed by radiation if needed. These steps directly target the cancer in the breast
- Hormone (endocrine) Therapy – technically hormone blocking therapy – after surgery, patients typically take medications such as tamoxifen or aromatase inhibitors. These drugs either block estrogen receptors or reduce the body’s estrogen production. They are usually taken for 5 to 10 years, significantly lowering the risk of cancer recurrence
- Chemotherapy (sometimes) – if the cancer is aggressive (as deemed “high risk” on a genomic test such asOncotype or MammaPrint), larger in size, or has spread to the lymph nodes, chemotherapy may be recommended in addition to hormone therapy. Menopausal status and age play a part in chemotherapy recommendations.
- CDK 4/6 inhibitors – very expensive pills that are used for stage 4 cancers and now are being used for high-risk early-stage hormone positive cancer. Doctors are starting to prescribe these medications such as ribociclib and abemaciclib when stage 2 or 3 breast cancers are felt to be high risk, including when cancer is found in the lymph nodes.
- Advanced or Metastatic (Stage 4) Disease – For hormone-positive cancers that spread beyond the breast, newer therapies are available. These include CDK4/6 inhibitors (pills) or sometimes PI3K inhibitors (also pills) and other targeted treatments that work hand in hand with hormone therapy to control cancer for longer.
What Makes Hormone-Positive Breast Cancer Different?
Compared to other types, such as triple negative breast cancer, hormone-positive cancers often:
- Grow more slowly
- Respond well to hormone-blocking medications (especially when ER percentage is high)
- Have more long-term treatment options
However, hormone positive breast cancers sometimes return many years after the first diagnosis. This delayed recurrence risk is one reason doctors recommend long-term hormone therapy.
What Can Patients Do?
Facing a diagnosis can feel overwhelming, but patients can take steps to feel more empowered:
- Ask about your receptor status (ER, PR, and HER2). Knowing these results helps you understand your treatment options
- Discuss your ER percentage with your oncologist. A higher percentage usually predicts stronger benefit from hormone therapy
- Talk with your doctor about side effects of hormone therapy. Hot flashes, bone health changes, or fatigue may happen, but there are many ways to manage them.
- Stay consistent with medication. Taking hormone therapy every day as prescribed, is one of the most effective ways to protect yourself.
- Keep a long-term outlook. Remember that treatment may last many years, but it is designed to keep you healthy and reduce your risk of cancer recurrence.
Key Takeaways
- Hormone-positive breast cancer means the tumor grows in response to estrogen or progesterone
- IHC testing reports ER staining from 0% to 100%. Strongly ER-positive tumors (close to 100%) respond better to hormone therapy (hormone blocking therapy) than tumors with only 1-2% positivity
- Long-term hormone therapy is essential to reduce recurrence risk and improve survival
- By understanding your receptor results and staying engaged in your care, you can make informed choices and feel more in control of the journey ahead.
