Oct. 28, 2004 Preventing prostate cancer and helping men with the disease avoid osteoporosis is the focus of two new clinical trials at the Medical College of Georgia.
MCG is participating in a national study to determine whether men can reduce their prostate cancer risk by taking a drug that halts the conversion of the male hormone to a super-duper hormone that appears to stimulate prostate cancer growth.
The lifetime risk of prostate cancer is about 1 in 6 for American men, except for blacks as well as men with a family history who are at increased risk, according to the National Prostate Cancer Coalition; the risk increases to about 50 percent by age 80.
MCG also is a study site for a national study looking at whether a new drug that slows bone resorption can help prostate cancer patients avoid osteoporosis.
The cancer prevention study examines the potential of dutasteride, the active ingredient in a drug marketed to treat prostate enlargement, a common problem of aging.
“While there is no direct relationship between prostate enlargement and prostate cancer, both cancerous and benign growth of the prostate appear to be stimulated by this super hormone called dihydrotestosterone,” says Dr. James A. Brown, MCG urologist specializing in prostate cancer. For some unknown reason, circulating male hormone, testosterone, is converted into this more potent male hormone in the prostate gland and scalp. “What is neat about that is if you can prevent that conversion … you are taking away a potent stimulator of cell growth,” says the Georgia Cancer Coalition Distinguished Cancer Clinician and Scientist. “Many of the cells in the gland will atrophy and shrink away.”
For the prevention study, MCG is evaluating patients age 50-75 with elevated PSAs, a marker for prostate cancer, who have had a negative biopsy in the last six months. The study runs for four years and participants will receive additional biopsies at years two and four.
The osteoporosis prevention study looks at the bone-thinning disease often associated with menopausal women. Loss of the female hormone, estrogen, helps disrupt the normal balance between cells called osteoblasts that make bone and osteoclasts that consume it. While men also naturally experience a decline in their testosterone level with age, they keep making the hormone throughout life and tend to start out with denser bones than women, unless they get prostate cancer. Much like breast cancer, prostate cancer is a hormone-dependent cancer and a mainstay of treatment is hormone therapy. “Testicles make male hormone,” says Dr. Brown. “The prostate gland is a sex organ that responds to male hormone. This gland develops at puberty, with the influx of hormones, but it will often continue to grow throughout life, which is why sometimes with age, men have problems with an enlarged prostate. Cancer also will grow more rapidly and aggressively with male hormone circulating.”
Men often prefer that the testicles that produce male hormones not be surgically removed. The alternative is therapy that suppresses hormone production, essentially chemical castration to prevent signaling the testes to make hormone. “The mainstay of prostate cancer therapy is anti-hormone therapy and men typically are on it for years,” says Dr. Brown. Side effects often include markedly reduced libido as well as the increased risk of osteoporosis.
The study looks as a new bisphosphonate that slows bone resorption and may help correct the bone deficit that occurs with anti-hormone therapy, Dr. Brown says. For the study, MCG is looking for men with prostate cancer who are taking anti-hormone therapy for their disease. Participants will be followed for two years; half will receive the study drug and half will receive placebo. MCG expects to enroll about 20 patients in the study that will follow 1,200 men nationally.
Dr. Brown notes that in addition to new therapies still under evaluation, new treatment approaches already being used, such as laparoscopic and robotic surgery, are reducing the trauma and side effects of surgically removing a diseased prostate. The standard approach to removal has been about a six-inch vertical incision from the navel downward. Side effects include lost ability for a spontaneous erection and prolonged problems with incontinence. With five small incisions instead of one big one, the laparoscopic approach cuts post-surgical pain and recovery time. Less nerve damage also means men often regain continence more quickly and the minimally invasive approach appears to reduce the risk of ongoing erectile dysfunction, Dr. Brown says.
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