Prostate cancer treatment may
cause severe bone loss
PITTSBURGH -- June
4, 2001 (Cancer Digest) -- Men may be losing bone at an alarming
rate as a result of a commonly used treatment for prostate cancer,
a new study suggests.
The findings suggest
gonadotropin-releasing hormone agonists (GnRH-a), a frequently
used treatment for suppressing production of male hormones aimed
at slowing the spread of prostate cancer, causes severe drops
in bone mass and results in an increased risk of fracture in
men.
The researchers led
by Dr. Susan Greenspan at the University of Pittsburgh Medical
Center (UPMC) and colleagues at Beth Israel Deaconess Medical
Center published the research results in the June issue of the
Journal of Clinical Endocrinology and Metabolism. The results
may require doctors to monitor bone loss in these patients much
more closely.
"We were surprised
to find that men who were treated with GnRH-a for prostate cancer
experienced up to a decade's worth of bone loss within the first
year of therapy," senior author Greenspan stated in a press
release.
The prostate, found
only in men, is a walnut-sized gland located in front of the
rectum, at the outlet of the bladder. It contains gland cells
that produce some of the seminal fluid, which protects and nourishes
sperm cells in semen.
Male hormones stimulate
the prostate gland to develop in the fetus. The prostate continues
to grow as a man reaches adulthood. It will continue to grow
or at least is maintained after it reaches normal size throughout
the life of a man as long as male hormones are produced. If male
hormones are removed, the prostate gland will not fully develop
or will shrink.
GnRH-a works by depriving
the body of testosterone, an androgen hormone that increases
the growth of prostate tumors. However, testosterone also is
essential to maintaining bone mass in men.
While doctors have
been using GnRH-a for more than a decade in treating men with
late-stage metastatic prostate cancer, they have begun using
it more recently in men with earlier-stage disease and for longer
periods of time.
"In treating men
with this therapy earlier and for longer periods of time, we
are putting them in a menopause-equivalent condition and subjecting
them to severe osteoporosis -- a disease that may have more serious
consequences than early-stage prostate cancer," says Greenspan.
"With close to
200,000 men being diagnosed with prostate cancer each year, we
could be facing an enormous increase in the incidence of debilitating
bone fractures in men," she says.
In this study, investigators
compared bone mineral densities, biochemical markers of bone
turnover and body composition in 60 men with prostate cancer
-- 19 of whom were on GnRH-a and 41 who were not. The also examined
the same markers in 197 healthy men.
While the prostate
cancer patients who had not been treated with hormones had bone
loss markers that were similar to those of the healthy controls,
the scores of men treated with hormones showed marker levels
that were up to 17 percent lower than those of untreated men,
putting the treated men at a markedly higher risk for fracture.
Treated men also had
nearly double the levels of urinary marker for bone absorption,
indicating that their bones were disintegrating twice as quickly
as the bones of untreated men. In addition, they had significantly
lower blood counts and levels of estradiol, a hormone that is
needed, along with testosterone, for bone health. Treated men
also showed an increase in total body fat and loss of muscle
mass.
"Clearly, cutting
off testosterone production in men through the administration
of GnRH-a has some very serious consequences related to skeletal
integrity and overall health," says Greenspan. "This
is particularly troubling because the greatest degree of bone
loss appears to occur with the initiation of treatment."
Prostate cancer is
the second leading cause of cancer death in men in the United
States, exceeded only by lung cancer. The American Cancer Society
estimates that 31,500 men in the United States will die of prostate
cancer during 2001. Prostate cancer accounts for about 11% of
male cancer-related deaths.
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