Hormonal Therapy Patients Are at Risk for Bone Loss

Treatment, Monitoring Needed to Lessen Side Effect

Osteoporosis is generally thought to be an "old woman's disease," but bone loss could be a significant problem for breast cancer patients at any age.

"There are possibly two reasons for this," says Karin Hahn, M.D., an assistant professor in the Department of Breast Medical Oncology at M. D. Anderson.

"One, we usually do not recommend estrogen replacement therapy for breast cancer survivors whose bodies have stopped producing estrogen (when they go into menopause), and two, our cancer therapies may cause some women to become menopausal at an earlier age. Both of these situations put breast cancer patients at higher risk for bone loss because estrogen deficiencies increase bone loss."

The reason estrogen is not given to some menopausal breast cancer patients to offset osteoporosis is because estrogen may stimulate the growth of breast cancer cells in women whose tumors had sensitivity to estrogen/andor progesterone.

Some cancer treatments such as the aromatase inhibitors, Arimidex (anastrozole), Aromasin (exemestane) and Femara (letrozole), may increase bone loss by reducing estrogen levels in the body to prevent breast tumor growth. These drugs are commonly used in postmenopausal breast cancer survivors whose tumors were sensitive to estrogen.

Screening guidelines not standardized

Bone loss also can affect:

• All menopausal patients regardless of cancer type
• Any cancer patient receiving hormonal therapy

That includes people such as prostate cancer patients undergoing hormonal therapy. Patients at most risk of bone loss need a qualified internist, endocrinologist or rheumatologist to address, treat, and, in some cases, prevent bone loss, Hahn says. There are many causes of bone loss in addition to cancer therapy that need to be examined.

Hahn is working with colleagues to develop a standardized method of monitoring bone health in breast cancer patients. The American Society for Clinical Oncology (ASCO) recommends that any woman on aromatase inhibitors have a bone mineral density test annually. "We also recommend that all postmenopausal women be screened, regardless of their health status," Hahn says.

Correct diagnosis important

Some M. D. Anderson breast cancer patients with osteoporosis or osteopenia (thinning bone that hasn't yet reached the clinical threshold for osteoporosis) are referred to endocrinologists within the institution for treatment, including Rena Sellin, M.D., a professor in the Department of Endocrine Neoplasia and Hormonal Disorders.

Sellin says it's vital to consider all possible causes.

"We don't just look at the numbers (on the bone mineral density test) and give them a prescription," she says. "You may assume that the aromatase inhibitor is the problem, but it may be that the patient has hyperparathyroidism or a Vitamin D insufficiency."

Chronic use of corticosteroid medications as well as some other medications also can cause bone loss. Smoking cigarettes is also a risk factor for osteoporosis.

Although osteoporosis drugs do not rebuild lost bone, they can prevent further bone loss.

Bisphosphonates, a family of drugs used to prevent and treat osteoporosis, include Fosamax, Actonel and Boniva. The drugs suppress the activity of osteoclasts, cells that work to break down bone. Miacalcin (calcitonin) is a nasal spray that works in a similar fashion, but may not be as effective.

Sellin says newer drugs are geared toward rebuilding lost bone. Forteo, which is synthesized parathyroid hormone, is an injectable drug that forms new bone and increases bone mineral density.

Even with the available treatments, however, bone health is largely up to the individual. "Women need to make sure they're getting enough calcium and Vitamin D in their diet, as well as weight-bearing exercise such as walking or jogging," Hahn says. "This is especially important during their peak bone-building years, before age 35."