Types of Anti-Estrogen Therapy for Breast Cancer

Your breast cancer diagnosis probably raised a long list of questions. How big is the tumor? Is it aggressive? What do I do now?

One major factor that determines your treatment path is the hormone status of your cancer. Around 80% of women are diagnosed with estrogen receptor positive breast cancer, or ER+ breast cancer. For these cancers, estrogen encourages cancer cells to grow and spread.

Women with ER+ breast cancer are often prescribed anti-estrogen therapy, also called hormone therapy or endocrine therapy, which works by either preventing the production of estrogen or blocking estrogen from acting on your breast cancer cells. It’s designed to reach cancer cells anywhere in your body and is typically taken for 5 to 10 years after surgery. The type of anti-estrogen therapy you go through depends on the stage of your cancer, whether you’ve experienced menopause, and other health considerations.

Let’s break down the major types of anti-estrogen therapy for ER+, early-stage breast cancer patients.

Tamoxifen is typically prescribed to premenopausal women with early stage breast cancer. Rather than stopping estrogen production, tamoxifen limits the ability of estrogen to act on your tumor. For women with ER+ breast cancer treated with surgery, Tamoxifen can help lower the chances of recurrence and raise the chances of living longer.

Another common type of anti-estrogen therapy is known as aromatase inhibitors, or AIs.

Aromatase inhibitors are drugs that stop estrogen production in postmenopausal women. AIs differ from drugs like Tamoxifen in that they suppress estrogen production in the body instead of only blocking estrogen from binding to the receptors of the cancer cells. AI’s are not prescribed for pre-menopausal women whose ovaries are still producing estrogen.

For postmenopausal women, a small amount of estrogen is still made by an enzyme called aromatase, found in tissues like fat. AIs work by blocking aromatase, thereby stopping estrogen production.

estrogen receptor breast

There are three AIs that are reported to work equally well in treating breast cancer:

  • Letrozole (Femara)
  • Anastrozole (Arimidex)
  • Exemestane (Aromasin)

For post-menopausal women, taking these drugs, either alone or after Tamoxifen, has been shown to work better than taking only Tamoxifen.

For most ER+ post-menopausal women with breast cancer, many doctors recommend taking an AI at some point during therapy. Schedules that are known to be helpful include:

  • Tamoxifen for 2 to 3 years, followed by an AI to complete 5 years of treatment
  • Tamoxifen for 5 years, followed by an AI for 5 years
  • AI for 5 years – though with new emerging data your physician may recommend a longer duration

If you had early-stage breast cancer and were pre-menopausal when you started therapy, your doctor might recommend taking Tamoxifen first, followed by an AI if you go through menopause during your treatment.

Ovarian Suppression or Depletion is another way to deplete estrogen by utilizing surgery, radiation, or drug therapy to prevent the ovaries from making estrogen.

For premenopausal women, removing or shutting down the ovaries makes women undergo menopause. This not only limits estrogen, but may allow use of an AI. Ovarian ablation is most often done to treat metastatic breast cancer, but it is also considered in women with early-stages of the disease.

There are several ways to remove or shut down the ovaries:

  • Oophorectomy, which is the surgical removal of your ovaries, and radiation ablation, which prevents the ovaries from making estrogen, are permanent forms of ovarian ablation.
  • Next is luteinizing hormone-releasing hormone analogs, or LHRH for short. These drugs stop the signal that the body sends to the ovaries to make estrogen, causing temporary menopause. Common LHRH drugs include leuprolide (Lupron®) and goserelin (Zoladex®).
  • The last form of ovarian ablation is chemotherapy. Some chemo drugs can damage the ovaries so they no longer make estrogen.

While anti-estrogen therapy has been shown to be an effective way of helping prevent ER+ breast cancer from returning, it is important to understand that each of these treatment methods may come with side effects that can impact quality of life, as well as more serious health risks.  Discuss with your doctor to make sure you are choosing the right treatment path for you.

Article by:

Jeniffer Smith

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