Prostate cancer cells rely on the male hormones, androgens, ( of which testosterone is one) to grow. Reducing the levels of androgen circulating in the blood can often stop the growth of prostate cancer. There are a number of different treatments that can reduce the circulating androgen levels.

One of these is the use of drugs called LHRH analogues. The initials LHRH stand for leuteinising hormone-releasing hormone analogues. The levels of androgen in the blood are controlled by the pituitary gland. Leuteinising hormone (LH) is released by the pituitary gland and causes androgen levels to rise. Giving LHRH analogues causes the levels of LH to fall and this in turn leads to a fall in androgen levels.

Another way of reducing the effect of androgens on prostate cancer is to give drugs that act by binding on to hormone receptors on the prostate cancer cells themselves, thereby blocking the hormone from reaching, and stimulating, the cancer. These drugs are known as anti-androgens. They are given in tablet form and include Cyprostat (cyproterone acetate), Casodex (bicalutamide) Suprefact (buserelin) and Drogenil (flutamide).

At first it might seem that giving these two treatments together could improve the control of the cancer. This approach (known as 'maximum androgen blockade, or combined androgen blockade) has been quite widely used in the past. The results of clinical trials suggest, however, that only a small number of patients benefit from this combination. For the majority, the LHRH analogues alone are sufficient and avoid the possible extra side-effects the additional anti-androgens may cause.

Having said this, when LHRH analogues are first given they cause a very temporary increase in androgen levels, lasting between 5 to 12 days (this is often called an androgen flare). For this reason it is common practice to give anti-androgen tablets in addition to the LHRH injection, during the first few weeks of treatment.