Bone Loss
One of the “silent” side effects of breast cancer treatment is something that is not typically seen or felt by the patient—a decrease in bone density (or osteoporosis). Causing the bones to become fragile and thin, a decrease in bone density can lead to bone breaks, loss of height, severe back pain, permanent disability and even death if serious spinal or vertebral fractures occur.
Three common causes of bone density loss occur in breast cancer patients: the effect of chemotherapy on bone marrow blood cells, a drop in estrogen levels following chemotherapy and a side effect of taking aromatase inhibitors (AIs).
Chemotherapy targets rapidly-dividing cancer cells, damages blood cells in bone marrow tissues and prevents new ones from forming. The effect on bone marrow depends on the type of drug treatment, dosage, length of treatment, interval between treatments and physical condition of the patient.
Following chemotherapy, many breast cancer patients experience a drop in estrogen levels as ovaries stop functioning. Estrogen protects bones, so reduced or absent levels of the hormone can lead to bone density loss. Pre-menopausal women experience this as they enter menopause caused by chemotherapy.
According to Carolyn Hendricks, M.D., an oncologist specializing in breast cancer in private practice in Bethesda, Md., and a board member of Suburban Hospital Healthcare System in Bethesda, “The older a woman is at the time chemotherapy is administered, the higher the likelihood of premature menopause. Women under 35 who receive chemotherapy are very likely to regain normal menstrual function, but women over 45 are highly unlikely to regain normal menstrual function and are at increased risk of bone mass loss.”
AIs, hormonal therapies for post-menopausal women with estrogen-sensitive breast cancer, can also cause bone loss. Many breast tumors are estrogen sensitive—they grow when estrogen is present. Women with these tumors are prescribed estrogen-suppression drugs (such as AIs) to reduce the chances of relapse after their initial treatment. However, studies show that AIs can cause bone density loss because they block the production of estrogen.
Breast cancer patients should ask their doctor about blood and bone density tests to monitor bone health. Blood tests can determine a patient’s estrogen levels once treatment is completed. A bone density test can be done by a DEXA scan that measures bone density in critical areas of the body such as the hip joint and spine. It is a painless, non-invasive test that takes about 20 minutes. Dr. Hendricks suggests that a baseline DEXA scan be done for women who experience premature menopause and for post-menopausal women prior to starting AI therapy. Follow-up DEXA scans should be performed in women who lose bone mass. “In addition, changes in height or complaints of back pain should trigger oncologists to obtain X-rays to determine if a fracture is present,” she said.
This article was published in Lifeline.