How Does Tamoxifen Prevent Breast Cancer Recurrence?

Tamoxifen is Commonly Prescribed, But Has Potential Drawbacks

Tamoxifen tablets
Tamoxifen tablets. Credit: Karl D. Stephan

Tamoxifen, the generic form of Nolvadex, is one of the most commonly prescribed medications  to prevent breast cancer recurrence. While it has been proven to be effective, it does have side effects and drawbacks you should be aware of before starting treatment. 

What is Tamoxifen?

Tamoxifen is an antiestrogen, also known as an estrogen suppressor, medication, taken as a 10 or 20 mg tablet. It is a popular selective estrogen receptor modulator (SERM).

It's approved by the Food & Drug Administration (FDA) to treat: 

  • women and men diagnosed with hormone receptor-positive, early-stage breast cancer after surgery, chemotherapy or radiation to reduce the risk of recurrence
  • women and men diagnosed with advanced stage or metastatic, hormone receptor-positive disease

It is also used to reduce breast cancer risk in women who have not been diagnosed but are at a higher than average women risk for developing breast cancer. It is not effective on hormone receptor-negative cancers. 

Benefits of Taking Tamoxifen

Tamoxifen was approved in 1998 and has proven since then to be effective in treating breast cancer in millions of patients. It is still considered an excellent option for you if you are premenopausal or are postmenopausal and cannot take an aromatase inhibitor. It can decrease your risk of developing breast cancer again by up to 50%. It can also decrease the chances of you developing new cancer in your other breast by up to 50%.

It has other benefits as well. As a SERM, it can also help slow or stop bone loss and lower cholesterol levels. 

What Are the Drawbacks of Tamoxifen?

While tamoxifen is very effective, it does have significant side effects, including blood clots, stroke and can cause other forms of cancer. Because of these issues, it's important to discuss with your doctor your medical history and whether or not you smoke.

You should call your doctor if you have any of these symptoms:

  • abnormal vaginal bleeding
  • pain in the pelvis
  • leg swelling
  • chest pain
  • shortness of breath
  • weakness, numbness or tingling
  • vision issues

The most common side effects include increased tumor or bone pain, nausea, fatigue, mood swings, depression, headaches, hair thinning, constipation, dry skin and loss of libido. If any of these side effects impact you, be sure to discuss them with your doctor. 

How Long Do I Need to Take Tamoxifen?

Based on clear evidence from two large randomized phase III clinical studies (ATLAS and aTTom), a 10 year rather than a five year adjuvant treatment with Tamoxifen is associated with a smaller risk of recurrence and a reduction in breast cancer mortality.

Your doctor will recommend one of two options, based on your case. He or she will either administer Tamoxifen for 10 years, or administer Tamoxifen for five years and then switch to an aromatase inhibitor for five more years.

Is Tamoxifen Worth the Tradeoffs?

Weighing risks and benefits of taking tamoxifen may seem tricky, but most doctors agree that the benefits outweigh the risks. Be sure to discuss your symptoms with your doctor and share with him if you experience any side effects.

Keep the lines of communication open to ensure tamoxifen works for you without significant drawbacks. 

"Tamoxifen Revised Label". Food & Drug Administration. 2013. 

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