Frequently Asked Questions   /   Types of Cancer

Efficacy of Tamoxifen for Metastatic Breast Cancer

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Carolyn Vachani RN, MSN, AOCN
Last Modified: January 10, 2006

Dear OncoLink "Ask the Experts,"
How can you tell if the anti-cancer drug you are taking is working? For, example, I am taking Tamoxifen for metastatic breast cancer. How will I know if it is effective?

Carolyn Vachani, RN, MSN, AOCN, OncoLink's Nurse Educator responds:

In the case of most anti-cancer medications, the best way to know it is working (responding) is to see shrinking of the tumor. This may be seen by an imaging study, such as CT scan, MRI, bone scan or PET scan. Some tumors may be better followed by a blood test called a tumor marker, for example, CA125 levels can follow the response of an ovarian cancer (CA 27.29 levels can be followed in some breast cancer patients). Some cancers may be easily seen, such as a skin cancer, or felt under the skin. In that case, the patient and physician may be able to follow the response visually.

The next issue to address is how long should you wait to see a response? This depends on the medication being used. Hormone therapy, like Tamoxifen, can take several months before a response is seen. Some women will even have a “flare” of the tumor in the first 1-2 weeks on hormonal therapy – causing bone pain and redness of skin lesions (if they have skin lesions), which may seem like the medication isn't working. So patience is important with hormone therapy. One would expect a much quicker response to traditional chemotherapy (but also many more side effects).