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I take Arimidex® for my breast cancer, but I have read that it can cause bone loss and osteoporosis. What can I do?


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This is an important question because the National Cancer Institute estimates that one in eight women in our country will develop breast cancer during her lifetime. Anastrozole (Arimidex®) is in a class of drugs called aromatase inhibitors (AIs). Two other drugs in this class are exemestane (Aromasin®) and letrozole (Femara®). They are used to treat breast cancer and prevent its return in postmenopausal women.

While AIs are very effective treatments for breast cancer, drugs in this class can cause bone loss and an increased chance of breaking a bone. When women have estrogen sensitive-breast tumors, estrogen can cause the cancer to grow and spread. AIs help women with this type of cancer by reducing the estrogen levels in the body. Even though a postmenopausal woman already has low levels of estrogen, it is this additional decrease in estrogen that can cause bone loss.

AIs are different from other hormone related medicines used to treat breast cancer, such as tamoxifen. For example, tamoxifen does not cause bone loss in postmenopausal women, although it can cause bone loss in premenopausal women.

Before starting cancer treatment. Some healthcare providers recommend that women have a bone density test of the hip and spine before they start cancer treatment. The results of this test can serve as a baseline. When a bone density test is repeated in the future, it can be compared to the results of the baseline test to find out if any bone density has been lost. Women who have low bone density or osteoporosis should consider taking an osteoporosis medicine, such as a bisphosphonate, when starting treatment with an aromatase inhibitor. Women who develop low bone density or osteoporosis while taking an aromatase inhibitor should also consider starting an osteoporosis medicine. Osteoporosis medicines help prevent further bone loss and reduce the risk of breaking a bone.

Other tests that may be useful are blood and urine tests that show changes in bone turnover. These tests are sometimes called bone turnover marker tests or biochemical marker tests. The results of some of these tests, such as serum bone alkaline phosphatase or urine N-telopeptide, might increase during cancer treatment. This could be a sign that bone loss will occur and can suggest the need for an osteoporosis medicine.

Risk factors you can control. Other steps you can take to protect your bones during cancer treatment include having a balanced diet with fruits and vegetables and getting enough calcium and vitamin D. Adults under age 50 need 1,000 mg of calcium and 400 – 800 IU of vitamin D every day. Adults age 50 and older need 1,200 mg of calcium and 800 – 1,000 IU of vitamin D every day.

Both weight-bearing exercises and muscle-strengthening exercises can benefit your bones. Examples of weight-bearing exercises are walking and playing tennis. Examples of muscle-strengthening exercises are lifting weights or using elastic exercise bands. Inactivity and lack of exercise contribute to bone loss. Smoking and drinking too much alcohol are also bad for your bones.

Remember that if you have low bone density, your bones will break more easily. Older people especially should be aware of ways to prevent falls.

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