Estrogen receptor (ER) positive breast cancer

Overview

Estrogen receptor (ER) positive breast cancer is the most common type of breast cancer. ER positive means that the cancer cells have proteins called estrogen receptors. The hormone estrogen can attach to these receptors and help the cancer grow.

After breast cancer is diagnosed, the cancer cells are tested for estrogen receptors (ERs), progesterone receptors (PRs) and a protein called HER2. The results help your healthcare team learn more about the cancer and choose treatments that are most likely to work.

Hormone therapy, also called endocrine therapy, is often an important part of treatment for ER positive breast cancer. Hormone therapy for breast cancer, can block the effects of estrogen on the cancer or lower estrogen levels in the body. This can slow or stop the cancer from growing.

Types

ER positive breast cancer is a type of hormone receptor (HR) positive breast cancer. HR positive means that cancer cells have receptors for estrogen, progesterone or both. ER, PR and HER2 test results provide important information about the cancer and help guide treatment.

ER positive and PR positive

Most ER positive breast cancers also are PR positive. This means the cancer cells have receptors for both estrogen and progesterone. Hormone therapy is often an important part of treatment for these cancers.

ER positive and PR negative

Some ER positive breast cancers are PR negative. This means the cancer cells have estrogen receptors but don't have progesterone receptors. Because the cancer is ER positive, hormone therapy may still be an important part of treatment.

ER low positive

Some ER positive breast cancers have estrogen receptors in only a small number of the cancer cells. This is called ER low positive breast cancer. ER low positive breast cancers are considered ER positive, but they may respond differently to hormone therapy. There is less evidence about how much hormone therapy helps with these cancers.

HER2 status

ER positive breast cancer can be HER2 positive or HER2 negative. HER2 is a protein that helps cells grow. Testing shows how much HER2 the cancer cells have and helps guide treatment.

• ER positive, HER2-positive. These breast cancers have high levels of HER2 or extra copies of the HER2 gene. Medicines that target HER2 may be part of treatment.
• ER positive, HER2 negative. These breast cancers don't have high levels of HER2. HER2 test results, along with other features of the cancer, help your healthcare team choose treatment.

Symptoms

Estrogen receptor (ER) positive breast cancer can have the same symptoms as other types of breast cancer. Many people with early-stage breast cancer don't have any symptoms.

When symptoms happen, they may include:

• A new lump or thickened area in the breast or underarm.
• A change in the size or shape of the breast.
• Swelling of all or part of the breast.
• Changes in the skin of the breast, such as dimpling, thickening, scaling or a change in skin color.
• A nipple that turns inward or other changes in the nipple.
• Nipple discharge, especially if it is bloody.
• Breast or nipple pain that doesn't go away.

When to seek care

Make an appointment with a healthcare professional if you notice a new change or a change that isn't typical in your breast. Most breast changes aren't cancer, but it's important to have changes checked.

Don't wait for your next screening mammogram to have a breast change checked. Tell your healthcare team about a change even if a recent mammogram didn't find breast cancer. Your healthcare professional may recommend more tests to find out what's causing the change.

Causes

The exact cause of estrogen receptor (ER) positive breast cancer isn't known. Like other types of breast cancer, it starts when breast cells develop changes in their DNA. DNA contains the instructions that tell cells what to do. The changes cause the cells to grow and multiply when they shouldn't. Over time, these cells can form a tumor.

ER positive breast cancer cells have proteins called estrogen receptors. Estrogen can attach to these receptors and help the cancer grow.

Many factors can increase the risk of having breast cancer. But most people who get breast cancer don't have one clear cause.

Risk factors

A risk factor is something that increases the chance of getting breast cancer. Having one or more risk factors doesn't mean that you'll get estrogen receptor (ER) positive breast cancer. And some people who get breast cancer have no known risk factors.

Many risk factors linked to ER positive breast cancer also increase the risk of breast cancer in general.

Older age

The risk of breast cancer increases with age. Most breast cancers occur after age 50.

Hormone and reproductive factors

Some factors can increase how long breast tissue is exposed to estrogen. Longer exposure to estrogen is linked to a higher risk of breast cancer. These include:

• Starting your period at a younger age.
• Starting menopause at an older age.
• Never having given birth.
• Having your first child at an older age.

Menopausal hormone therapy

Taking menopausal hormone therapy can increase the risk of breast cancer. The risk is higher with treatment that contains both estrogen and progestin.

Inherited gene changes

Some gene changes passed from parents to children increase the risk of breast cancer. Certain inherited gene changes are more closely linked to ER positive breast cancer. One example is a change in the CHEK2 gene.

Other inherited gene changes, including changes in the BRCA1, BRCA2, ATM and CDH1 genes, increase the risk of breast cancer in general. Having an inherited gene change doesn't mean that you'll get breast cancer.

Family history

Having a blood relative with breast cancer increases your risk. Examples of blood relatives are parents, grandparents and cousins. The risk may be higher if more than one blood relative has had breast cancer or if a blood relative was diagnosed at a younger age.

Personal health history

Having had breast cancer increases the risk of developing another breast cancer. Certain breast conditions also increase the risk of breast cancer. These include atypical ductal hyperplasia, atypical lobular hyperplasia and lobular carcinoma in situ (LCIS).

Dense breasts

Having extremely dense breasts increases the risk of breast cancer. Dense breast tissue also can make breast cancer harder to see on a mammogram.

Excess weight after menopause

Having excess weight after menopause increases the risk of breast cancer.

Alcohol

Drinking alcohol increases the risk of breast cancer. The risk increases with the amount of alcohol you drink.

Not being physically active

Not getting enough physical activity is linked to a higher risk of breast cancer.

Radiation exposure

Having radiation therapy to the chest at a young age, such as to treat lymphoma, increases the risk of breast cancer later in life.

Complications

Complications can happen with estrogen receptor (ER) positive breast cancer. These include:

• Cancer that comes back. ER positive breast cancer may come back after treatment. This is called recurrent breast cancer. It may come back in or near the breast or in another part of the body, such as the lungs, liver or bones. Cancer that comes back in another part of the body is called metastatic cancer.
• Infertility. ER positive breast cancer treatment may include chemotherapy, which can make it harder to get pregnant after treatment. Not everyone with ER positive breast cancer needs chemotherapy. If you want to have children in the future, talk about this with your healthcare team before treatment starts. Your team may refer you to a fertility specialist who can explain your options. These options might include freezing eggs, freezing embryos and other ways to preserve fertility.
• Lymphedema. Surgery or radiation therapy that affects the lymph nodes may cause lymphedema. Lymphedema is swelling caused by a buildup of fluid. It most often affects the arm on the side of the body where breast cancer was treated.

Prevention

There's no sure way to prevent estrogen receptor (ER) positive breast cancer. But there are things you can do that may lower your risk.

• Ask about breast cancer screening. Talk with your healthcare professional about when to start screening. Your risk factors can help determine which screening tests you may need. If you have dense breasts and other risk factors, your healthcare professional may recommend a breast MRI in addition to a mammogram. Ask about the benefits and risks of each test. Together, you can decide which screening plan is right for you.

  Screening doesn't prevent breast cancer. But it may help find breast cancer early, when treatment is more likely to be successful.

• Know what's typical for your breasts. You may choose to check your breasts sometimes to learn how they usually look and feel. This can make it easier to notice a new lump or other change. Tell your healthcare professional about any changes you notice.
• Maintain a healthy weight. Having excess weight, especially after menopause, increases the risk of breast cancer. If you need help reaching or maintaining a healthy weight, talk with your healthcare professional.
• Be physically active. Aim for at least 30 minutes of physical activity on most days of the week. If you haven't been active lately, start slowly and ask your healthcare professional for guidance.
• Avoid or limit alcohol. Drinking alcohol increases the risk of breast cancer. The more alcohol you drink, the greater the risk. If you choose to drink alcohol, limit how much you drink.
• Consider breastfeeding. If you have a baby, breastfeeding may lower the risk of breast cancer. Consider breastfeeding if you want to and are able to.

If you have a family history of breast cancer, talk with your healthcare team about your risk. Genetic counseling and genetic testing may help find inherited gene changes that increase the risk of breast cancer.

Some people at high risk of breast cancer may choose to take medicine to help lower their risk. Talk with your healthcare team about whether this may be an option for you.