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Anti-androgens are another class
of hormone therapy drugs that are used in prostate
cancer treatment. Anti – androgens affect
the receptors of the prostate cells’ nuclei and
prevent the reception of testosterone. These anti-hormone
drugs are sometimes used as monotherapy
for prostate cancer patients who are in early stages
with low risk tumor features. Anti - androgens may also
be used in conjunction with either surgical or medical
castration to ablate 100 percent of the body’s
testosterone.
Anti - androgens work by blocking
the testosterone receptors in the prostate cells. Normally,
testosterone would bind with these receptors and fuel
the growth of prostate cancer cells. Some researchers
believe that men with a higher number of hormone receptors
will more quickly experience hormone
refractory cancer, which occurs when
the prostate cancer cells grow resistant to the hormone
deprivation. With the receptors blocked, testosterone
cannot “feed” the prostate. Anti - androgen
therapy does not eliminate testosterone and therefore
may have fewer or less severe side effects than those
associated with surgical and medical castration.
When patients stop benefiting from the use of anti-androgens,
some patients have found stopping hormone therapy to
be effective for combating prostate cancer. This phenomenon
is referred to as the “anti – androgen withdrawal
effect.” For this reason, some doctors will use
intermittent hormone therapy, where patients use the
drugs until their levels drop then stop, then begin
the drugs again when testosterone levels rise. Other
doctors prescribe six months on and six months off as
intermittent therapy.
The three most common anti - androgen
drugs used for prostate cancer hormone therapy are flutamide,
bicalutamide,
and nilutamide.
These drugs are taken orally as either a tablet or a
pill. A single dose usually contains between 50 mg and
150 mg, depending on the patient’s needs and doctor’s
prescription. Doctors encourage their patients to take
the drug around the same time everyday to ensure a steady
stream of therapy. Patients who forget to take a dose
and are close to a time where they usually take the
next dose, should not take a double dose. Taking a dose
around the same time each day will decrease the incidence
of some side effects, such as nausea or vomiting.
Hormone therapy can involve unpleasant
and, in more rare cases, dangerous side effects. Because
there are multiple anti - androgen drugs available in
United States as well as Canada and the United Kingdom,
patients with serious side effects should speak with
their doctors about possibly changing drugs. Some doctors
may change the form of hormone therapy, but in other
cases doctors will encourage their patients to continue.
In some cases, the side effects will dissipate as the
body gets used to the drug and the androgen ablation.
The use of castration in addition
to anti - androgens is called combined
androgen blockade (CAB). The use of
anti - androgens a few weeks before LHRH agonists are
started has been shown to significantly reduce the incidence
of hormone
flare that can be painfully dangerous
for patients with distant bone metastasis.
Anti – androgens can also be used after surgical
or medical castration stops being effective. There are
a few studies that indicate using anti - androgens as
monotherapy
may be slightly less effective than medical or surgical
castration as monotherapy. Other studies found no difference
in the survival rates of people who had used only one
form of treatment.
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