|
Prostate cancer hormone therapy
is the systemic ablation of the body’s testosterone
which, for a period of time, will slow or stop the growth
and spread of prostate cancer. Hormone therapy may also
be called androgen deprivation or androgen ablation.
The Role of Hormones in
Prostate Cancer
The male sex hormone, testosterone, causes the growth
of the prostate gland and other sex organs in the developing
male. Even as men pass through the age of puberty, testosterone
continues to contribute to the growth of the organ.
Testosterone will fuel the growth of any prostatic cell:
the chemical cannot discriminate between the receptors
of healthy tissue and cancerous tissue. Prostate cancer
hormone therapy removes the chemical that “feeds”
cells and can stop or slow the growth and spread of
the tumor.
Where does Testosterone
Come From?
A chemical sequence in the brain signals the testicles,
which make 90% of the body’s hormones, to begin
production. A structure in the brain called the hypothalamus
continually monitors the blood stream for adequate levels
of testosterone. If these levels drop, the hypothalamus
releases a chemical called GnRH (gonadotropin releasing
hormone) or LHRH (luteinizing hormone releasing hormone).
GnRH acts as a messenger and travels to the pituitary
gland where it plugs into designated receptors.
The pituitary gland receives the
message from the hypothalamus and releases Gn (gonadotropin)
or LH (luteinizing hormone). Gonadotropin travels through
the blood stream and stimulates the production of hormone
in the testicles. Testosterone plugs into the receptors
of the cells’ nuclei and helps them grow. The
other 10 percent of testosterone is produced by the
adrenal glands which are located close to the kidneys.
How is Hormone Therapy Administered?
There are four basic methods androgen deprivation: castration,
estrogen, anti – androgens, and combine androgen
blockade.
Castration uses orchiectomy, LHRG agonists, and LHRH antagonists to remove testicle-produced
testosterone from the body. Orchiectomy surgically removes
the testicles, while LHRH agonists and antagonists block
the messenger process in the brain. A castrate level
refers to having 90 to 95% testosterone less than that
of a healthy male.
Estrogen is not commonly used to
treat prostate cancer because the synthetic version
– diethylstilbestrol – has been shown to
cause serious cardiovascular problems. Estrogen is the
female sex hormone and cannot feed the prostatic tissue,
but the hypothalamus will mistake estrogen for testosterone
and stop GnRH production.
Anti-androgens fill in the receptors
of the cells. Testosterone circulates through the body
but cannot interact with the prostate gland.
Combined androgen blockade uses
both castration and anti-androgens to ablate
testosterone 90% of testicle-produced hormone and to
block the prostate’s ability to receive the hormone.
Methods of Delivering Prostate
Cancer Hormone Therapy
Today, treatment is administered as neoadjuvant, adjuvant,
and salvage therapy. Neoadjuvant is used before the
primary treatment to shrink the prostate gland to an
acceptable volume. Adjuvant is used while patients are
undergoing treatments. Salvage is used when a primary
treatment has failed.
Androgen ablation may also be used
intermittently, for example, in periods of 6 months
on and 6 months off. Some doctors believe intermittent
therapy staves off the hormone refractory prostate cancer,
which occurs when the disease stops responding to treatment
and begins to grow again.
|
