Frequently Asked Questions from Patients Undergoing Endocrine Therapy

What are the advantages of endocrine therapy?

If the breast cancer is hormone-receptor positive, you usually will be offered endocrine therapy. If the cancer is not hormone-receptor positive, you will not benefit from endocrine therapy and it will not be offered. Endocrine therapy is as effective as or even more effective than chemotherapy at preventing breast cancer from coming back or controlling cancer growth. Endocrine therapy usually is better tolerated than chemotherapy.

What are the side effects of endocrine therapy?

The side effects depend on the drugs being used: tamoxifen or the aromatase Inhibitors or AIs (anastrozole, letrozole or exemestane).

In general, some possible side effects from tamoxifen include:

  • Hot flashes
  • Vaginal changes, such as increased discharge or dryness
  • In women still having periods, tamoxifen can cause periods to stop or become irregular
  • In women who have stopped having periods, tamoxifen can sometimes cause overgrowth of the uterine lining (Very rarely, tamoxifen causes a cancer of the uterus. This is usually easy to detect and treat.)
  • In women who have stopped having periods, tamoxifen improves bone density
  • Very rarely, tamoxifen can cause a blood clot in the leg or lung, or in the brain (a stroke)

In general, some possible side effects for the AIs include:

  • Hot flashes
  • Vaginal changes such as increased dryness
  • Loss of bone
  • Reversible aching of the bones and joints

Many patients do not experience many side effects from endocrine therapies, and the side effects are usually reversible. If you are experiencing side effects, your medical oncologist often can work with you to try another drug that you may tolerate better.

How long will I need to remain on endocrine therapy if I am being treated after surgery for breast cancer?

Research is still being done to help us understand how long patients need to be on endocrine therapy. In general, the recommendation is for at least five years. Some patients may need to be on endocrine therapy for 10 years.

How important is it to remain on endocrine therapy if I am being treated after surgery for breast cancer?

It is very important that you take endocrine therapy as recommended. Studies suggest that missing as little as 10 percent of the drug (three days a month) can start to increase your risk of breast cancer returning.

If you find that you have trouble taking your medication because of:

  • Cost
  • Not remembering
  • Side effects

Please discuss this with your cancer team. We can help with all of these.

What if I decide not to take endocrine therapy or I stop it after a while?

Endocrine therapy is as effective as or sometimes more effective than chemotherapy at preventing breast cancer from coming back or at controlling cancer growth. Not taking it as recommended puts you at a higher risk for breast cancer recurrence.

However, sometimes the risk of breast cancer coming back is low enough that a patient will decide that this risk is outweighed by side effects or other concerns. This is a very personal decision, and we encourage you to discuss it with your cancer team before making a decision.