This is the fourth and last part of our mini-series about the condition based on our patient booklet “Fast Facts for Patient and Their Supporters: Metastatic Prostate Cancer”.
What Is Happening in Your Body before Treatment
To understand how metastatic prostate cancer is treated, it helps to understand what is happening in your body before treatment. Testosterone is essential for prostate cancer growth. The figure below shows how testosterone is produced.
The progression of disease can therefore be delayed for several years, sometimes more, by stopping testosterone from reaching prostate cancer cells. This is achieved by surgical or chemical castration. “Castration” can be a frightening term, so ask your doctor to explain it fully. The figure below shows how hormone therapy and surgery works in this respect.
Surgical removal of both testicles, or the part of the testicles that make testosterone, is a simple day case procedure, often performed under local anesthesia. It involves a small incision in the middle of the scrotum, which is then closed with absorbable sutures. The relatively few complications of surgery such as bruising, blood clots and poor wound healing are easily managed. Over the next few hours your testosterone level will drop rapidly.
LHRH Agonists and Antagonists
These drugs are usually given as injections or implants into your arm, stomach area, thigh or bottom. Some LHRH agonists are available as a small pellet that is implanted under your skin under local anesthetic. The implant releases a constant dose of the drug for 1, 3 or 6 months.
LHRH agonists initially raise the testosterone level before it drops to castrate levels. This is called a testosterone “flare”. Because of this, a few patients experience a tumor “flare”, causing increased bone pain or worsening of urinary symptoms and an increased risk of spinal cord compression.
Treatment with anti-androgen tablets, starting a couple of weeks before your first LHRH agonist injection and continuing for a few weeks afterwards (4–6 weeks total) will help to avoid this.
LHRH antagonists can be administered without anti-androgens and are particularly beneficial if you have a high volume of spinal metastases and need rapid tumor control without a testosterone flare. Long-term use of LHRH antagonists can cause heart problems, but as these drugs are usually given intermittently this does not tend to be an issue.
Testosterone drops to the same levels as those in patients who have surgery.
Although the testicles produce most of the testosterone in the body, a very small amount is also produced by the adrenal glands. Anti-androgens, taken daily as tablets, stop the testosterone that is produced by the adrenal glands from reaching prostate cancer cells.
These drugs can be taken:
- on their own
- before LHRH agonist treatment
- together with LHRH agonist treatment (maximal androgen blockade)
- after orchidectomy.
Intermittent Hormone Therapy
When PSA levels continue to rise despite continuous anti-androgen therapy, you may be offered intermittent hormone therapy instead. This involves stopping treatment when your PSA level is low and stable, and starting treatment again when your PSA starts to rise. At present, researchers do not know whether continuous or intermittent therapy is better, but intermittent therapy has the added benefit of decreasing the side effects of therapy.
Normally, the adrenal glands produce hormones that are essential for the metabolic processes of your body. So, when you are taking antiandrogens, you will need to take other steroids to supplement the adrenal hormones that are no longer produced.
Information based on Metastatic Prostate Cancer (Karger, 2017).