Hormone therapy is also called androgen deprivation therapy (ADT) or androgen suppression therapy. The goal is to reduce levels of male hormones, called androgens, in the body, or to stop them from affecting prostate cancer cells.
Androgens stimulate prostate cancer cells to grow. The main androgens in the body are testosterone and dihydrotestosterone (DHT).
Most of the androgens are made by the testicles, but the adrenal glands (glands that sit above your kidneys) also make a small amount. Lowering androgen levels or stopping them from getting into prostate cancer cells often makes prostate cancers shrink or grow more slowly for a time. But hormone therapy alone does not cure prostate cancer.
When is hormone therapy used?
If the cancer has spread too far to be cured by surgery or radiation, or if you can’t have these treatments for some other reason
If the cancer remains or comes back after treatment with surgery or radiation therapy
Along with radiation therapy as initial treatment if you are at higher risk of the cancer coming back after treatment (based on a high Gleason score, high PSA level, and/or growth of the cancer outside the prostate)
Before radiation to try to shrink the cancer to make treatment more effective
Types of hormone therapy
Several types of hormone therapy can be used to treat prostate cancer.
Treatments to lower androgen levels
Drugs that stop androgens from working
Androgens have to bind to a protein in the prostate cell called an androgen receptor to work. Anti-androgens are drugs that bind to these receptors so the androgens can’t.
Drugs of this type include:
They are taken daily as pills.
Anti-androgens are not often used by themselves in the United States. An anti-androgen may be added to treatment if orchiectomy or an LHRH agonist or antagonist is no longer working by itself. An anti-androgen is also sometimes given for a few weeks when an LHRH agonist is first started to prevent a tumor flare.
An anti-androgen can also be combined with orchiectomy or an LHRH agonist as first-line hormone therapy. This is called combined androgen blockade (CAB). There is still some debate as to whether CAB is more effective in this setting than using orchiectomy or an LHRH agonist alone. If there is a benefit, it appears to be small.
In some men, if an anti-androgen is no longer working, simply stopping the anti-androgen can cause the cancer to stop growing for a short time. Doctors call this the anti-androgen withdrawal effect, although they are not sure why it happens.
Enzalutamide (Xtandi) is a newer type of anti-androgen. Normally when androgens bind to their receptor, the receptor sends a signal to the cell’s control center, telling it to grow and divide. Enzalutamide blocks this signal. It is taken as pills each day.
Enzalutamide can often be helpful in men with castrate-resistant prostate cancer. In most studies of this drug, men were also treated with an LHRH agonist, so it isn’t clear how helpful this drug would be in men with non-castrate levels of testosterone.
Other androgen-suppressing drugs
Estrogens (female hormones) were once the main alternative to orchiectomy for men with advanced prostate cancer. Because of their possible side effects (including blood clots and breast enlargement), estrogens have been replaced by other types of hormone therapy. Still, estrogens may be tried if these other hormone treatments are no longer working.
Ketoconazole (Nizoral), first used for treating fungal infections, blocks production of certain hormones, including androgens, similarly to abiraterone. It is most often used to treat men just diagnosed with advanced prostate cancer who have a lot of cancer in the body, as it offers a quick way to lower testosterone levels. It can also be tried if other forms of hormone therapy are no longer working.
Ketoconazole also can block the production of cortisol, an important steroid hormone in the body, so men treated with this drug often need to take a corticosteroid (such as prednisone or hydrocortisone).