Newly diagnosed breast cancer patients may be surprised to learn that there is not one, but several types of breast cancer. Learning about the different types and subtypes of breast cancer can be very helpful for understanding treatment options, prognosis, and more. Each type of breast cancer behaves and acts differently and may require different forms of therapy.

When a tumor is biopsied, a doctor called a pathologist will examine the sample to determine the cancer’s subtype. This information will be included in the pathology report. You can ask your doctor for a copy of this report for your records. One of the more common types of breast cancer you’ll see on a report is ER-positive (ER+).

What is ER+ cancer?

ER+ breast cancer simply means that a woman’s tumor cells have receptors that signal cancer cells to grow in response to estrogen. Estrogen is a hormone produced naturally in the body. An important strategy to prevent ER+ cancer from returning is to block estrogen from reaching those cells.

According to the American Cancer Society, 2 out of every 3 breast cancers are hormone-dependent. Most ER+ cancers are also PR+, meaning they grow in response to the hormone progesterone. But this isn’t always the case.

Studies have shown that ER+ breast cancer has the best prognosis of all the breast cancer subtypes and in some cases will not require chemotherapy after surgery. However, all breast cancers have the potential to return after primary treatment is completed. For this reason, women with ER+ cancers are typically given a medication to prevent cancer relapse.

Treatment for ER+ cancer

Treatment will start out in much the same way as it does for women with other types of breast cancer. Surgery, either a lumpectomy or mastectomy, will be performed to remove the tumor. If necessary, chemotherapy and radiation will be given afterward.

Once the tumor is removed and all other treatments are completed, you’ll be prescribed an anti-hormonal drug to reduce the risk of the cancer’s return. These drugs are usually taken orally at home. In most cases it is recommended that these drugs be taken for five years. However, one study suggests that these drugs should be given for 10 years to further reduce the chances of recurrence. The length of time you take these drugs will depend on your age and risk of recurrence.

Types of drugs

There are two classes of these anti-estrogen drugs. Each works to prevent cancer in a different way: One blocks the estrogen from stimulating the estrogen receptors on breast cancer cells, and the other stops the body from producing estrogen altogether.


Traditionally, tamoxifen is given to premenopausal women to block estrogen receptors on breast cancer cells. Although not without side effects, this class of drug is relatively safe and has been in use for more than 30 years. The most common side effects are mood swings, bone aches, vaginal dryness, and hot flashes. It can also cause thickening of the uterus and in rare cases, uterine cancer and blood clots. Follow up with your doctor when on these drugs, and report any unusual symptoms.

Aromatase inhibitors

Another class of these drugs is aromatase inhibitors, which are used in postmenopausal women. After menopause the ovaries are no longer producing estrogen and these drugs block the production of estrogen by non-ovarian sources. The most common of these are letrozole (Femara), anastrozole (Arimidex), and exemestane (Aromasin). These drugs can also cause bone and joint pain and increase your risk of osteoporosis, but not clots or uterine thickening.

Ovarian oblation

Another option for ER+ breast cancer treatment is ovarian ablation. This can be done with drugs, such as leprolin (Lupron), with radiotherapy, or with an actual surgical procedure. The surgery, called an oophorectomy, is the removal of the ovaries. An oophorectomy is a major surgery that can have a profound and permanent effect on a woman’s life, so it should be considered carefully.

In recent years, studies have shown that ovarian ablation in combination with aromatase inhibitors are more effective than tamoxifen for premenopausal women with hormone-positive breast cancer, and this has become the standard of care.

Estrogen blockers and metastatic cancer

Estrogen blockers can also be very effective at controlling ER+ metastatic cancer. For these patients, chemotherapy may not be effective and combination hormonal blocking agents are considered first-line therapy. These blockers may also have fewer side effects than other forms of chemotherapy, and can be a viable option when dealing with a relapse and/or metastasis.

Understanding your options is an important part of making treatment decisions. ER+ cancers have been well-studied and hormonal blocking drugs are an important part of treatment and reduce the risk of cancer recurrence after primary treatment. Understanding your treatment options will help to ensure the most effective treatment for you.