Men who reach retirement age with slow-growing prostate cancer are likely to live as long as men without tumours, scientists have discovered.

Only those with fast-growing or higher-grade tumours may die earlier, possibly losing between four and eight years off their life expectancy.

These findings, made by the University of Connecticut, could affect the way that prostate cancer is treated, particularly among men who have "low-grade" tumours. Most doctors still believe that early diagnosis and treatment usually involving radiation and radical surgery can improve survival rates.

But the new research endorses earlier findings that such aggressive intervention is of little or no benefit to many with the cancer. Even those with higher-grade tumours may still be better without having radical surgery, as the years lost may not outweigh the significant problems associated with treatment, which sometimes results in impotence and incontinence.

The study team tracked 451 men, aged between 65 and 75 years, with prostate cancer for 15 years. During that time, 154 died of prostate cancer, 221 died of other causes, 36 died of unknown causes and 40 were still alive. Nearly half of those diagnosed with high-grade cancer had died within 10 years, and the remainder died within 15 years. Just 9 per cent of those with low-grade cancer had died after 15 years.

Tumours are defined using a measurement called the Gleason score. Low-risk cancers fall within a Gleason score of two to four, medium-risk rates between five to seven, and highest-risk scores between eight and 10. Find out your score so you can help assess your own risk (JAMA, Aug 23, 1995).