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
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
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