Hormone Receptor Status in Breast Cancer

Hormone receptor status is important in determining options for breast cancer treatment. Determining your tumor's status is a high priority after a breast biopsy or breast-cancer surgery (mastectomy or lumpectomy). Whether you're positive (meaning estrogen and/or progesterone drives the growth of cancer cells) or negative (meaning hormones do not drive growth) will have a big impact on the next steps you take.

Hormone Receptors & Receptor Tests

All breast cancers are examined under a microscope for biomarkers of estrogen and progesterone receptors. About 70% of breast cancers are hormone receptor-positive.1

Your hormone receptor status should appear on your pathology report after biopsy or surgery. Receptors will be retested if you ever have a recurrence or metastases as well, as your status can change.

Hormones and receptors go together kind of like a lock and key. Receptors are proteins on the surface of breast cells, and when hormones bind to them, the receptors tell the cells to grow and divide.2 All breast cells have receptors, but they are found in much greater numbers on breast cancer cells that are considered positive.

A goal of treatment is to block the signal created when the hormones attach to receptors.3 Doing that requires one of two things:

1. Reducing the amount of the hormone in the body
2. Blocking the receptor so that hormone can't bind with it

Most of the time, breast cancers tend to be positive or negative for both estrogen and progesterone receptors.4 Now and then, one will be positive for estrogen but not progesterone. The treatment is the same either way.

Hormone Receptor Status Scores

Your report will show the percentage of cells that tested positive for hormone receptors.5 Zero percent means no receptors were found and 100 percent means all the tested cells had receptors.

Why Your Hormone Status Matters

Breast cancers that are estrogen receptor-positive (ER+) and/or progesterone receptor-positive (PR+) are "fueled" by hormones. They're different from breast cancers that are HER2-positive,6 in which tumor growth is driven by growth factors that bind to HER2 receptors on the cancer cells. Breast cancers that don't have any of these receptors are called triple-negative.7

Some breast cancers are both hormone receptor-positive and HER2-positive, meaning that estrogen, progesterone, and growth factors can stimulate cell growth.8 These cancers are often referred to as triple-positive breast cancers.

If the only information you're given is that your hormone status tests are negative, it's good to ask your healthcare provider for a number that indicates the actual score. Even if the number is a low one, the tumor may effectively be treated with hormone therapy.

Treatment Options

If your tumor is ER+ and/or PR+, hormonal therapy is usually recommended.9 The choice of medications, however, depends on your menopausal status.

Before menopause, the ovaries produce the greatest amount of estrogen. To prevent this estrogen from fueling your cancer cells, medications called selective estrogen receptor modulators are used. These drugs, such as tamoxifen,10 bind to the estrogen receptor so that estrogen can't get to it.

After menopause, the situation is different because you have a lot less estrogen in the body. The primary source of post-menopausal estrogen is your body's conversion of androgens (male-type hormones) into estrogen.11 This reaction is catalyzed by an enzyme known as aromatase. Medications called aromatase inhibitors can block this enzyme so your body can't produce estrogen, thus starving the tumor.

Three aromatase inhibitors12 are available:

• Arimidex (anastrozole)
• Aromasin (exemestane)
• Femara (letrozole)

These drugs may sometimes be used in pre-menopausal women after ovarian suppression therapy. After first taking medications that prevent the ovaries from making estrogen or, in some cases, have their ovaries removed, these women are switched from tamoxifen to an aromatase inhibitor. This strategy appears to give some a better survival advantage.

Bisphosphonates can be used along with aromatase inhibitors for early-stage post-menopausal ER+ breast cancers as well.13 This appears to reduce the risk of recurrence and especially the spread of breast cancer to the bones.

Other hormonal therapies may be used at times, too. A drug called Faslodex (fulvestrant) is a selective estrogen receptor down-regulator (SERD).14 It's sometimes used to treat women whose cancer progresses while they're on tamoxifen or an aromatase inhibitor. In addition, other hormonal therapies for metastatic breast cancer may be considered for some people.

Length of Treatment

In the past, treatment with tamoxifen or aromatase inhibitors was usually continued for five years. Studies have shown, though, that in women with a high risk of recurrence, longer treatment can be beneficial.15 It's important to talk to your healthcare provider about current recommendations for length of treatment in light of these new studies.