Conformal beam radiotherapy allows radiotherapy to be given in a more targeted way. So, men having this treatment for prostate cancer generally have fewer side effects than with conventional external beam radiotherapy.

Because of this the National Institute for Health and Clinical Excellence (NICE) state in their guidance on Improving outcomes in urological cancers (September 2002) that conformal radiotherapy is the best way to give external radiotherapy for prostate cancer and should be made available to patients.

Standard external beam radiotherapy is carefully planned so that beams are directed to the prostate gland from three or four different positions. Radiation is concentrated on the prostate gland with as little as possible going to the bladder and bowel which are nearby. But, some radiation still reaches them and can cause bladder irritation (cystitis) and diarrhoea.

Conformal radiotherapy improves on this technique by using a computer to shape the radiotherapy beam to the outline of the prostate gland. This reduces the amount of radiation that reaches the bowel and bladder. And, so reduces side-effects.