Harvard Health Letter

By the way, doctor: Tamoxifen versus aromatase inhibitors

Q. I've had an ER-positive breast cancer tumor removed. Now I am getting ready for follow-up therapy. I've heard that the aromatase inhibitors are better than tamoxifen. What is your opinion?

A. Breast cancer is classified according to whether it has receptors for the female hormone estrogen. If the cancer has estrogen receptors — or, as cancer specialists say, it is estrogen-receptor (ER) positive — estrogen can stimulate the cells to grow and divide, resulting in more cancer. About two-thirds of all breast cancers are ER-positive. The good news is that ER-positive tumors tend to be less aggressive than those that are ER-negative, so the prognosis tends to be quite a bit better. Still, blunting the effects of estrogen is important for preventing recurrence.

As you indicated, there are two main types of anti-estrogen medications: tamoxifen (Nolvadex), which blocks the ability of estrogen to stimulate cancer cell growth, and the aromatase inhibitors, which deplete the production of estrogen. The FDA has approved three aromatase inhibitors: anastrozole (Arimidex), exemestane (Aromasin), and letrozole (Femara).

To continue reading this article, you must login.
  • Research health conditions
  • Check your symptoms
  • Prepare for a doctor's visit or test
  • Find the best treatments and procedures for you
  • Explore options for better nutrition and exercise
Learn more about the many benefits and features of joining Harvard Health Online »