An oxygen treatment given to divers with the "bends" is to be tried out on cancer patients suffering side effects of radiotherapy.

Hyperbaric oxygen therapy involves sitting in a sealed chamber and breathing pure oxygen while the air pressure is slowly increased.

The treatment is used to tackle decompression sickness in divers, and to help injured elite footballers heal more quickly. Doctors hope it will also alleviate unpleasant side effects associated with radiotherapy for cancer in the pelvic region. Those include cancers of the cervix, ovaries, prostate, testicles, bowel, bladder and womb.

Most patients return to normal within a few weeks of stopping radiotherapy treatment but about 30 per cent develop long-term problems that can interfere with their daily lives, including diarrhoea, stomach cramps and frequent bowel movements.

Seventy-five patients will take part in the HOT (hyperbaric oxygen therapy) II trial at specialist centres in London, Cardiff, Chichester, Great Yarmouth, Hull, Plymouth and the Wirral.

One of the scientists leading the trial, Professor John Yarnold from the Institute of Cancer Research and the Royal Marsden Hospital, said: "It's very difficult for patients who have already suffered through cancer and radiotherapy treatment to be left with these debilitating side effects. We hope to answer once and for all whether hyperbaric oxygen therapy will improve their quality of life."