In prostate cancer, hormones are used to control testosterone levels. By stopping/reducing testosterone supply, or preventing it reaching prostate cancer cells and therefore restricting their growth, even if the cancer has metastasised. Over 90% of testosterone in the male body is produced in the testicles; testosterone is also produced in the adrenal gland above the kidneys.
Hormone therapy can treat prostate cancer wherever it has metastasised, whether local or advanced. It doesn’t cure cancer but shrinks it or delays its development – sometimes for years. Hormone therapy does not cure cancer but helps to slow its progression. It is sometimes used to shrink the cancer in preparation for radiotherapy, or may be used concurrently. If there is a risk after conclusion of radiotherapy that the cancer may still metastasise, hormone therapy may be continued afterwards for up to six months.
There are several methods employed to impede testosterone reaching the prostate; these can be in the form of tablets to prevent testosterone reaching the prostate, injections or implants to prevent production of testosterone, or orchidectomy (removal of the testicles, or that part of the testicle which produces testosterone).
LHRH agonists (luteinising hormone-releasing hormone) come in the form of implants (zoladex) or injections (prostap, decapeptyl). They are preceded by a course of anti-androgen tablets to prevent the body over-producing testosterone as an initial reaction to beginning LHRH agonist therapy (this is a normal reaction), and therefore to prevent the cancer being able to grow. This course generally lasts two weeks, and is initiated one week before commencing LHRH agonist therapy.
Anti-androgens may also be used separately as hormone therapy in their own right, as they prevent testosterone from reaching the cancer cells. Another hormone used to treat prostate cancer is oestrogen, which slows the cancer’s growth, and kills some cancer cells; it also acts on the testicles, preventing their release of testosterone. This is not a common treatment because of its side effects, such as DVT, CVA and hypertension.
If LHRH agonists are not effective on their own, a ‘maximal androgen blockade’ may be initiated; this involves using an anti-androgen as well as the LHRH agonist. This is not first-line treatment because with the extra drug come extra side effects.
Patients on hormone therapy will have their PSA monitored regularly. Sometimes intermittent hormone therapy is used, this relies on regular PSA results. The patient is given hormone therapy when the PSA is high and when it decreases, the therapy is stopped temporarily. Trials continue, but it is thought that outcomes are the same as those for continuous therapy, but without so many of the side effects.
Hormone therapy for prostate cancer can have significant side effects because of the decreases in testosterone, such as increasing the risk of developing osteoporosis, diabetes, and heart disease. It can also cause erectile dysfunction and loss of libido, hot flushes, gynaecomastia, fatigue and muscle atrophy. Bone density can start to deterioriate within the first six months of treatment with LHRH agonists (although this has not been linked with anti-androgen treatment). Therefore patients need to be encouraged to eat a healthy diet with plenty of fruit and vegetables, being careful to ensure daily intake of 10-20mg vitamin D and 1000-1500mg calcium. Regular exercise is also encouraged, three 30-minute sessions per week is ideal, particularly weight-bearing exercise such as walking, running, or weights. Smoking cessation should be promoted. To reduce the risk of developing heart disease or diabetes it is particularly important to reduce alcohol intake and salt, ensuring a good diet and a healthy lifestyle.
Erectile dysfunction (ED) and loss of libido is a common side effect, about 50% of men undertaking prostate treatment will encounter one or both of these. ED is more likely to be caused by LHRH agonist (stopping the production of testosterone) rather than anti-androgens.
Many patients also experience hot flushes; these can be minimised by attempting to maintain an even temperature, by avoiding spicy foods, using a fan to cool the room, and wearing lightweight clothes, particularly cotton/linen. Consumption of soy products may help, as will stopping smoking.
Some patients will find that on hormone therapy they put on weight, lose muscle tone, or fatigue more easily; exercise is important to counteract these.