Hormonal therapy treats prostate cancer by removing the supply or blocking the action of male hormones such as testosterone that encourage prostate cancer growth. Hormonal therapy slows the growth of the cancer and reduces the size of the tumour(s).
Hormonal therapy can be used as:
- Monotherapy - where one type of hormonal therapy is used on its own
- Combination Therapy (CAB/MAB/TAB) – where two different types of hormone therapy are used together e.g. a LHRHa and an anti-androgen
Hormonal therapy can also be used in combination with other types of treatment e.g. radiotherapy or prostatectomy. - Neoadjuvant hormone therapy when it is given before prostatectomy or radiotherapy, to reduce the size of the prostate.
- Adjuvant hormone therapy when it is used after prostatectomy or radiotherapy to kill any cancer cells that remain following these procedures.
Hormonal control can be achieved by surgery (orchidectomy) to remove the testicles (the main source of testosterone) or by medicines. There are two main types of hormonal medicines:
- Luteinizing Hormone-Releasing Hormone agonist – LHRHa
- Non-Steroidal Anti-androgens
Other hormonal agents which may be used to treat prostate cancer include female sex hormones (oestrogens) e.g. stilboestrol and steroidal anti-androgens e.g. cyproterone acetate.
An LHRHa is a luteinizing hormone-releasing hormone agonist (e.g. goserelin – ‘ZOLADEX’ or leuprolide), which produces medical castration. They work by ‘switching off’ the production of male hormones from the testicles by reducing the levels of a hormone called luteinizing hormone. This hormone is produced by the pituitary gland (a pea-sized gland located at the base of the brain which regulates and controls the release of hormones which directly or indirectly affect most basic bodily functions).
LHRHa’s work just as well as an orchidectomy but do not involve surgery. They are used as monotherapy or combination therapy (with an anti-androgen) for advanced disease. They are also used in combination with prostatectomy or radiotherapy as neoadjuvant or adjuvant therapy, where goserelin has been shown to be very effective.
They are given by injection either under the skin (subcutaneous) or into the muscle (intra-muscular). The injections are generally given every month or every 3 months, although in some countries longer acting preparations are available.
Non-steroidal anti-androgens (e.g. bicalutamide – ‘CASODEX’, flutamide), block the action of testosterone and therefore prevent it from working. They do this by attaching themselves to proteins (receptors) in the cancer cells.
They are used in combination therapy (with and LHRHa) in advanced disease. Bicalutamide 150mg is also used as monotherapy in locally advanced disease where it has been shown to be as effective as medical or surgical castration. It is also used in combination with prostatectomy or radiotherapy as adjuvant therapy for locally advanced disease.
They are taken orally, as tablets.
Two different types of hormonal agents e.g. an LHRHa plus a non-steroidal anti-androgen, are used together to increase the effect on the tumour.
Combination therapy not only prevents the action of testosterone produced by the testes but also the small, but important amount, which is produced by other glands i.e. the adrenal glands. Such therapy is sometimes called Complete Androgen Blockade (CAB), Maximal Androgen Blockade (MAB) or Total Androgen Blockade (TAB)
In advanced disease a combination of an LHRHa (e.g. goserelin) plus and non-steroidal anti-androgen (e.g. bicalutamide) can be used. Clinical trials identify that men treated with such combination therapy may live longer than those treated with an LHRHa alone.
Most men who undergo medical or surgical castration will experience a loss of sexual desire and impotence. In addition, hot flushes frequently occur. Surgery is permanent and the effects cannot be reversed. However, medical castration is potentially reversible. If treatment is stopped, testosterone is produced once again.
Compared to castration, non-steroidal anti-androgens are less likely to reduce sexual desire or to cause impotence and may therefore be preferred by many men. Similarly they are less likely to cause hot flushes. However, some men will notice tenderness and/or enlargement of their breasts, when anti-androgens are used as monotherapy.
Management options for these possible side effects are available, please discuss these with your doctor. Symptoms are usually reversible and the effect of testosterone returns when treatment is stopped. |