ER- and PR-Positive Breast Cancer

Some breast cancer cells have unique characteristics that can be precisely targeted during treatment for heightened effectiveness. Known as hormone-positive breast cancer, these tumors grow in response to certain hormones, such as estrogen and progesterone. ER-positive breast cancer cells have estrogen receptors, and PR-positive breast cancer cells have progesterone receptors. Although a breast tumor can have both, one or no hormone receptors, most breast cancers have at least one, and approximately 80% are ER-positive or ER/PR-positive.

The hormone receptor status of breast cancer is an important consideration when planning treatment. If a breast tumor has one or both hormone receptors, certain drugs can be used to keep estrogen and/or progesterone from attaching to the receptors, which in turn can help keep the cancer from growing and spreading. At Tampa General Hospital’s Cancer Institute, we thoroughly test each newly diagnosed breast cancer patient to determine whether their tumor has hormone receptors that are fueling its growth. Using these and other details, the acclaimed team in our Breast Cancer Center can develop a highly personalized treatment plan to help the patient achieve the best possible outcome and quality of life.

What Are Receptors?

Found on the surface of various cells, receptors are proteins that bind to certain substances in the blood. Healthy breast cells and some breast cancer cells have receptor proteins that attach to estrogen and progesterone. Once attached to the respective hormones, the receptors become activated and change the expression of certain genes to stimulate cell growth.

Estrogen vs. Progesterone

Estrogen and progesterone are steroid hormones that occur naturally in the body. Estrogen is produced by the ovaries of premenopausal women, the skin and fatty tissues of women of all ages and the brain and testes of men. Progesterone is produced by the corpus luteum—a temporary gland formed by a remnant of an ovarian follicle in the latter half of the menstrual cycle—of premenopausal women, and by the adrenal glands of men.

In women, estrogen stimulates the development of female sexual characteristics, while progesterone prepares the uterine lining for conception and pregnancy. In men, estrogen promotes erectile function and bone health, while progesterone facilitates the production of sperm and testosterone. Estrogen and progesterone play a vital role in sexual development and reproductive health, but they also promote the growth of hormone-sensitive cancers.

What Causes ER-and PR-Positive Breast Cancer?

Researchers have identified several factors that may play a role in the development of hormone-receptor-positive breast cancer. These include:

  • Obesity
  • Elevated hormone levels
  • Polycystic ovary syndrome (PCOS)
  • Hormone replacement therapy
  • The use of diethylstilbestrol (DES) during pregnancy
  • Prenatal exposure to DES
  • Klinefelter syndrome

When one or more of these factors is present and cancer develops, estrogen or progesterone can serve as a spark that causes the cancerous cells to multiply and spread.

How Are ER- and PR-Positive Breast Cancer Diagnosed?

If breast cancer is suspected based on the symptoms or the results of an imaging scan, a physician will typically order a breast biopsy, which involves obtaining a small sample of suspicious tissue for evaluation under a microscope. As part of this process, a pathologist will test the tumor tissue for hormone receptors. The most common test used to classify the hormone receptor status of breast cancer is an immunohistochemistry (IHC) test, which is sensitive enough to identify a hormone-positive tumor even if only 1% of the tested cells have a hormone receptor.

In addition to estrogen and progesterone receptors, breast cancer is usually tested for human epidermal growth factor receptor 2 (HER2), another protein that promotes the growth of cancer cells. Luminal A and luminal B tumors, which originate in the inner (luminal) cells that line the milk ducts, tend to be ER-positive and HER2-negative.

How Are ER- and PR-Positive Breast Cancer Treated?

Hormone therapy may be used in combination with surgery or as a standalone treatment for hormone-positive breast cancer. One common option is tamoxifen, a drug that blocks the hormone receptors in cancer cells. The goal is to lower the level of estrogen and/or progesterone in the body and thereby inhibit the growth of the cancer.

Benefit From World-Class Care at TGH

At TGH, we offer groundbreaking hormone therapy for ER- and PR-positive breast cancer, as well as the latest options in surgery, chemotherapy and radiation therapy. If would like to talk with an expert on our team, contact us at (800) 844-4554 to request an appointment.