The use of an anti-androgen and
a form of castration is called Combined
Androgen Blockade or CAB. Combined
androgen blockade may also be called combined hormone
blockade or total hormone blockade. During prostate
cancer hormone therapy, the most common form of CAB
is an anti-androgen which is started a few weeks before
a Luteinizing Hormone-releasing Hormone agonist (LHRH). LHRH
agonists by themselves will cause hormone
flare which can be painful, or deadly,
or both for patients with advanced prostate
cancer with distant bone
metastasis.
The hormone flare triggered by the
LHRH agonist is a reaction that causes the body to flood
with testosterone for 7 to 10 days. Since testosterone
can help prostate cancer grow, many patients, even those
in earlier stages of less aggressive prostate cancer,
may prefer to avoid hormone flare. Anti – androgens
block the body’s ability to use testosterone,
so the flood of testosterone never reaches the prostate
gland. This form of combined androgen blockade is common
for patients in later stages of prostate cancer. Hormone
flare is not dangerous to early stage prostate cancer
patients nor will hormone flare incite a more aggressive
growth of their prostate cancer.
Castration, both the surgical orchiectomy
and the medical LHRH agonist and LHRH antagonist, will
eliminate only 90 to 95 percent of the body’s
testosterone. Some doctors may recommend that their
patients opt to ablate 100% of the testosterone. Castration
affects only the testosterone produced by the testicles,
not the adrenal glands located near the kidneys. Taking
an anti-androgen in addition to surgical or chemical
castration will prevent the prostate cancer from taking
up the remaining 5 to 10 percent of testosterone.
Sometimes, when orchiectomy, LHRH
agonists, or LHRH antagonists are no longer effective
for slowing the growth of prostate cancer, the use of
an anti-androgen will keep prostate cancer hormone therapy effective
for a longer period of time. The anti-androgen withdrawal
effect is where the prostate cancer cells who have adapted
to no testosterone are stopped by the reintroduction
of testosterone. Anti-androgen withdrawal may have some
effect with patients who are using combined androgen
blockade.
Estrogen is sometimes used with
prostate cancer hormone therapies. The use of lower
dose estrogen may lessen the severity or the occurrence
of side effects caused by castration or anti-androgens.
As a prostate cancer treatment,
there is much controversy surrounding the use of combined
androgen blockade (CAB). There are studies that suggest
that patients who opt for combined androgen blockade
as their prostate cancer treatment have slightly higher
overall survival rates than those who have used castration
or anti –androgens alone. These studies also indicate
that combined androgen blockade has higher biochemical
relapse free survival rates when compared to anti-androgens or castration alone. Other studies suggest
the opposite: patients who opt for combined androgen
blockade have a slightly lower overall survival rates
than those who opt for castration or anti – androgens
alone.
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