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Hormonal therapy for prostate cancer
Hormonal therapy is a systemic therapysystemic therapyTreatment that travels through the bloodstream to reach cells all over the body. that slows the growth and spread of prostate cancer cells by changing hormone levels or blocking their receptors in the body. Hormones are chemical substances that are produced by glands in the body or made in a laboratory. Drugs, surgery or radiation therapy can be used to change hormone levels.
Hormonal therapy may be used:
- as the primary treatment for advanced or recurrent prostate cancer
- after surgery in men with locally advanced disease to destroy cancer cells left behind and to reduce the risk of the cancer recurring (adjuvantadjuvantTreatment given in addition to the first-line therapy (the first or standard treatment) to help reduce the risk of a disease (such as cancer) coming back (recurring). hormonal therapy)
- before, during and after radiation therapy in men who have high-risk prostate cancer and in some men with intermediate-risk disease
- to relieve pain or to control the symptoms of advanced prostate cancer (palliative therapy)
The type of hormonal therapy used and the doses and schedules of drugs vary from person to person.
Hormone therapy is not a cure, but 70%–85% of men receiving hormonal therapy will respond to the treatment for a period of time. Eventually, the response will decrease and the prostate cancer will begin to grow.
Different strategies are used to give hormonal therapy:
- early hormonal therapy versus delayed hormonal therapy – The choice is between starting hormonal therapy early before any symptoms of disease progression are seen or delaying hormonal treatment until symptoms are seen. Both early and delayed androgen deprivation therapy (ADT) have benefits and risks. There is no firm evidence to show that one approach is better than the other.
- intermittent hormonal therapy – The hormonal therapy is given intermittently. The PSA level is used to monitor the cancer. This approach is believed to minimize the side effects of ADT. There is no firm evidence to show that this is better than continuous hormonal therapy.
- continuous hormonal therapy – ADT is given continuously. This is the common hormonal therapy standard.
- total hormonal blockade – This strategy is also called combined hormonal blockade. In this method, men are treated with both androgen deprivation (orchiectomy or an LHRH agonist) and an anti-androgen. There is not enough evidence to confirm the benefit of this approach.
Types of hormonal therapy
The growth of prostate cancer cells depends on androgens, the male hormones that cause male characteristics (such as deep voice and facial hair). The main androgens are testosterone and dihydrotestosterone (DHT). They are produced mostly in the testicles. Hormonal therapy is used to block the production or effects of these hormones. This treatment is also called androgen deprivation therapy (ADT).
The most common hormonal therapies used to treat prostate cancer are:
- luteinizing hormone–releasing hormone (LHRH) agonists
- LHRH antagonists
- surgery to remove the testicles (orchiectomy)
Luteinizing hormone–releasing hormone agonists
Luteinizing hormone–releasing hormone (LHRH) is produced by the hypothalamus gland. It stimulates the pituitary glandpituitary glandThe main endocrine system gland at the base of the brain that produces hormones to control other glands and many body functions, including growth. to produce luteinizing hormone (LH), which in turn stimulates the testicles to produce testosterone.
LHRH agonists are drugs that stimulate the pituitary gland to produce more LH. Eventually, the pituitary gland stops responding to the overstimulation, and this causes the testicles to stop producing testosterone. The reduction in testosterone stops the prostate cancer cells from growing.
When LHRH agonists are first taken, they cause a temporary rise in testosterone that lasts for about a week. This rise may result in a temporary worsening of symptoms for those with locally advanced or advanced disease, which is called a tumour flare reaction. During the flare reaction, men may have more urinary difficulties or bone pain. The doctor may prescribe anti-androgensanti-androgensTreatment with drugs that stop the production or block the actions of androgens (male sex hormones). for a period of time to reduce the symptoms of the flare.
LHRH agonists are given as an injection. Depending on the drug, injections are given every month or every 3 or 4 months. The drug is continued for the rest of the man’s life, even when the prostate cancer progresses. It should never be stopped.
The most common LHRH agonists are:
- leuprolide (Lupron, Lupron Depot, Eligard)
- goserelin (Zoladex)
- buserelin (Suprefact)
- triptorelin (Trelstar)
Luteinizing hormone–releasing hormone antagonists
LHRH antagonists are drugs that block the pituitary gland from producing luteinizing hormone (LH). This causes the testicles to stop producing testosterone. The reduction in testosterone stops the prostate cancer cells from growing.
The LHRH antagonist used to treat prostate cancer is degarelix (Firmagon).
Anti-androgens work by blocking the effects of testosterone on the prostate cancer cells. The drug attaches to androgen receptors on the prostate cancer cells and prevents them from using the testosterone in the bloodstream.
Anti-androgens may be given for a short time to a man who is taking LHRH agonists to reduce the worsening symptoms and pain caused by these drugs (tumour flare reaction).
Anti-androgens are given by mouth in pill or liquid form. The most common types are:
- flutamide (Euflex)
- bicalutamide (Casodex)
- nilutamide (Anandron)
- abiraterone acetate (Zytiga)
- enzalutamide (Xtandi)
If prostate cancer stops responding to anti-androgens, and the cancer begins to grow again, anti-androgen therapy is stopped. In some men, stopping anti-androgen therapy may cause an anti-androgen withdrawal response, in which the prostate cancer shrinks and the PSA levels drop. The cause of this response is unknown.
Estrogens are female hormones that lower the level of androgens. They are sometimes used when the prostate cancer stops responding to other hormone treatments.
Orchiectomy is the surgical removal of the testicles. It is a form of hormonal therapy. The testicles are the body’s main sources of testosterone. When they are removed, 90%–95% of the testosterone in the body is reduced. Prostate cancer tumours will quickly shrink when the level of testosterone drops.
An orchiectomy is a simple procedure:
- Local anesthetic is used to numb the scrotum.
- The doctor makes a small incision in the scrotum and removes the testicles.
- The scrotum appears smaller after surgery.
The advantage of orchiectomy is that the man does not require frequent drug injections. The disadvantage is that most men may feel that the removal of their testicles makes them less masculine. Because of this, most men choose to have their hormonal therapy given through drugs. The testicles get much smaller with any form of hormone therapy, so the actual appearance of the scrotum is not much different with surgery or drug therapy.
For more detailed information on specific drugs, go to sources of drug information.