May 14, 1999
Intermittent hormone therapy for prostate cancer helps preserve bone mass density
It takes just nine months on male hormone suppression treatment for men with prostate cancer to lose a significant amount of bone mass density — a rate comparable to the loss experienced by post-menopausal women, according to new research conducted at the University of Washington School of Medicine.
The study, presented May 16 at the American Society of Clinical Oncology meeting in Atlanta, is the first to document the rate of bone loss associated with combination hormone suppression. It also shows that an “intermittent” on-off schedule slows or reverses the loss of bone density during the off-treatment period, says Dr. Celestia Higano, lead researcher of the study and associate professor in the UW departments of medicine and urology.
Because men who have a rising level of PSA (prostate specific antigen) in the blood test that measures this protein — produced by both normal and cancerous prostate tissue — may live for many years, Higano designed a study to avoid the long-term harmful effects of continuous androgen (male hormone) suppression. It is well known that men with low testosterone have an increased incidence of osteoporosis, but the rate at which this occurs is unknown. The study followed 18 men whose bone mass density was measured before treatment, after nine months of treatment and at the end of the period off treatment. After nine months, the men lost an average of 4.3 percent of bone density in the lumbar spine and 2.5 percent in the hip — rates comparable to those seen in postmenopausal women. After stopping treatment, the rate of loss generally slowed or reversed in six patients with available measurements.
More than 30 percent of patients who have had surgery or radiation for early prostate cancer will subsequently experience a rising level of PSA. Extensive testing often does not show where the recurrent cancer is located, indicating that it exists in microscopic amounts. Although the treatment is considered controversial, many patients and doctors choose androgen suppression because it causes the abnormal PSA level to improve or disappear.
Androgen suppression treatment is widely known to cause loss of sex drive, impotence and hot flashes, but UW researchers have documented many other side effects. In a study of intermittent androgen suppression published in 1996, Higano described weight gain, fatigue, loss of muscle mass, moodiness, higher blood pressure and worsening diabetes relating to the treatment. She noted that these side effects improved when treatment was temporarily stopped. In addition, overall quality of life was improved, as had been previously reported by her colleagues at the British Columbia Cancer Agency in Vancouver.
“Physicians treating men with androgen suppression drugs need to be aware of the effects of this treatment on bone density,” says Higano. “But before jumping to conclusions, much more research needs to be done.”
In a future trial, she plans to study intermittent androgen suppression in combination with a drug that can treat osteoporosis and may also prevent spread of prostate cancer to the bones, the most common site for this cancer to grow.
