Your Cancer Answers: What about loss of bone mass?

Question: A frequent question that comes up from our breast cancer patients is whether they need to be concerned about osteoporosis?

Osteoporosis is the loss of bone mass which can result in bone fractures, most commonly in the lumbar vertebrae (lower back) and hips. Osteoporosis is most common in post menopausal women due to the low estrogen levels. Typically estrogen levels drop significantly when a woman goes through menopause, however, in our breast cancer patients, we often see a drop in their estrogen levels as a result of treatment they may have undergone for their breast cancer.

Generally, once a woman is diagnosed with breast cancer, any hormone replacement therapy they may have been on for treatment or prevention of osteoporosis is stopped, with the concern that this may stimulate the growth of the breast cancer.

Chemotherapy used to treat the breast cancer, even in premenopausal patients, can result in suppression of ovarian function and, therefore, lowered estrogen levels and an increased risk of osteoporosis. In younger ladies this ovarian suppression may reverse over time, in patients who are closer to menopause, their estrogen levels may remain low indefinitely (which is usually desirable with regards to breast cancer).

Aromatase inhibitors (Arimidex, Femara, Aromasin) inhibit estrogen production from the adrenal glands in post menopausal women (the ovaries are the primary source of estrogen in the premenopausal women, while the adrenal glands sever this role in post menopausal women). While these drugs are very effective in the treatment and prevention of breast cancer, they can also increase the risk of osteoporosis.

To monitor for risks of osteoporosis, we perform bone density scans (Dexa Scans). One should be performed as a baseline, and then repeated every one or two years. The frequency of repeated Dexa Scans depends on the results, the risk the patient carries, and whether they are on hormonal therapy for breast cancer or treatment for osteoporosis.

All women can do certain things to decrease their risk fractures including taking adequate amounts of vitamin D and calcium (800 to 1,000 international units of vitamin D and 1,000 to 1500 mg of calcium daily), as well as having a small amount of sun exposure routinely. There is no clear data on any particular diet which will decrease the risk of osteoporosis. However, exercising for 30 minutes three times per week has clearly been shown to be of benefit.

Occasionally, patients will require treatment for their osteoporosis. If so, bisphosphonates (drugs that lower bone re-absorption) are used either orally (drugs such as Actonel, Boniva, Fosamax) or intravenously (Reclast, Zometa). These drugs are generally tolerated well, however, can cause some stomach upset, and occasionally flu–like illnesses. A complication known as osteonecrosis of the jaw (bone loss in the jaw, which can result in serious complications) is very rare, but serious. Therefore, all patients on these medications must inform their dentist.

As with most situations, good communication between the doctor and the patient can result in excellent management of osteoporosis, but being aware of risks is the first step.

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