Progesterone Receptor Positive Breast Cancer (PR+)

Progesterone receptor-positive breast cancer (PR-positive breast cancer) has special receptors that bind to the hormone progesterone. That means it needs progesterone to grow. By depriving the cancer of progesterone, healthcare providers can stop it from growing.

Healthcare providers test breast cancer cells for hormone receptor status to help plan your treatment. They do this by taking a sample of the cancer and then examining it in a lab. If at least 1% of the cells in the sample have progesterone receptors, the lab report will say the cancer is PR positive (PR+).

Types of PR-positive breast cancer

While checking for progesterone receptors, healthcare providers also check for estrogen receptors. Cancer cells that are positive for either type are called hormone receptor-positive breast cancer.

PR-positive breast cancer may be:

• Positive for progesterone receptors and estrogen receptors (PR+/ER+) (this is more common)
• Positive for progesterone receptors alone (PR+/ER-) ( this is less common)

In general, testing positive for one or both hormone receptors improves your outlook (prognosis). The more hormone receptors breast cancer has, the more dependent it is on those hormones to grow. That makes hormone therapy more effective against it. PR+/ER+ breast cancer has a better prognosis than PR+/ER-.

Symptoms of PR-positive breast cancer

PR-positive breast cancer doesn’t cause unique symptoms. General breast cancer symptoms include:

• A breast lump that you can see or feel
• A change in the size or shape of your breast
• A change in the look or feel of the skin on your breast
• Nipple discharge
• Swelling or thickening in your armpit
• Breast pain

Why would any breast cancer cells have progesterone receptors on them?

Breast cancer cells are abnormal breast tissue cells. As normal breast cells often have hormone receptors, breast cancer cells may, too. Normal breast cells use hormones like estrogen and progesterone to grow and develop breast tissue, especially during female reproductive cycles.

Male breasts also respond to estrogen and progesterone, although in smaller degrees. That’s why male breast cancer can also be hormone receptor-positive. As normal breast cells have receptors for both hormones, it’s not clear why some breast cancers only have receptors for one, but not the other.

How doctors diagnose PR-positive breast cancer

To test breast cancer for hormone receptors, your healthcare provider must first take a sample. They’ll do this with a breast biopsy or by surgically removing the whole tumor (lumpectomy). Then, they’ll send the sample to a lab. They’ll test the sample using a technique called immunohistochemistry (IHC).

This test will tell them if the cancer is PR-positive or ER-positive, or both. It may also tell them other things, like what percentage of the cells have receptors, and other details. Your provider will explain what these details mean. They’ll use these test results to design your treatment plan.

How is PR-positive breast cancer treated?

Healthcare providers treat PR-positive breast cancer with hormone therapy that suppresses estrogen and progesterone in your body. Because progesterone depends on estrogen to work, targeting estrogen effectively blocks both hormones. 

Hormone therapies include:

• Aromatase inhibitors (exemestane, letrozole)
• Estrogen receptor antagonists (fulvestrant)
• Ovary suppressants (leuprolide, goserelin)
• Selective estrogen receptor modulators (tamoxifen, raloxifene)

Your treatment plan may also include:

• Breast cancer surgery
• Chemotherapy
• Radiation therapy
• Targeted therapy

What can I expect if I have PR-positive breast cancer?

Treatment for PR-positive breast cancer will likely include therapies that suppress estrogen and progesterone in your body. Suppressing these hormones may cause symptoms similar to menopause. Most people take these medications for at least five years to make sure breast cancer doesn’t return.

Hormone therapy can be very effective against PR+/ER+ breast cancer. It’s less effective against PR+/ER- breast cancer, but it still plays a role. Being able to use hormone therapy at all improves your prognosis. But many things affect your prognosis. Your provider is the best person to explain what you can expect.