The usual type of radiotherapy given to relieve pain from prostate cancer which, has spread to the bones is called external beam therapy. This involves lying on a bed, under a special radiotherapy machine which delivers a beam of powerful x-rays to the painful area. Treatment is painless, lasts only a few minutes and can be done as an out-patient. Often a single treatment is all that is needed to get good pain control. Side-effects are generally mild with possibly a little sickness and tiredness for a day or so after treatment. The treatment can be repeated if necessary. Also if there are several painful sites quite large areas can be treated at a single treatment (this is called hemibody irradiation).

In the last decade radioactive strontium has become available as an alternative to external beam radiotherapy. The radioactive strontium is injected, as a small amount of clear fluid, into a vein. The strontium is then taken up in the bones and gives off radiation to tumour seedlings in the bone with only a small dose of radiation reaching other tissues. All the bones take up the strontium, whether or not they have seedlings of prostate cancer, and it does give a moderate dose of radiation to the bone marrow. This means it cannot be regularly repeated, nor can it be used for people whose bone marrow has been damaged by other illnesses or treatments.

Radioactive strontium certainly can ease bone pain in prostate cancer but there is no clear evidence that it is any better than normal external beam radiotherapy. The situations where radioactive strontium might be considered are if there are multiple sites of pain throughout the body that cannot be covered by hemibody radiotherapy or if external beam radiotherapy, and other painkilling measures, have failed to control the bone pain.

Some very recent research has suggested that giving strontium together with chemotherapy might improve the outcome. More clinical trials will be needed before doctors will be able to decide whether combining these two types of treatment really does give a worthwhile benefit.