Older men with early stage prostate cancer may live longer if doctors treat them with radiation or surgery instead of the usual approach of watchful waiting, a new study suggests.

Doctors often hold off on surgery for older men with prostate cancer because the disease progresses slowly and they may face a higher risk of dying of some other cause.

But research published in Wednesday's Journal of the American Medical Association found men with the cancer who were treated had a 31 per cent lower risk of dying over 12 years compared with those who were only observed.

"Studies have shown that low- and intermediate-grade prostate cancers may grow slowly, and many patients may never suffer complications from their disease," said the study's lead author, Dr. Yu-Ning Wong, a medical oncologist at the University of Pennsylvania in Philadelphia.

"This makes decisions regarding treatment complicated for patients and their families."

In the observational study, Wong and his colleagues looked at survival from active treatment with radiation or surgical removal of the prostate gland compared with observation for 44,630 men aged 65 to 80.

The men were diagnosed between 1991 and 1999 and survived more than a year after the diagnosis. They were followed up until death or the end of the study in 2001.

The preliminary new findings suggest that men who are 75 to 80 may also benefit from treatment for prostate cancer.

The results need to be validated by rigorous randomized control trials of elderly men with localized prostate cancer before doctors consider the findings in their treatment decisions, the researchers cautioned.

"Improvement in the quality of care for men with prostate cancer may best be achieved not by treating more patients but by treating them more discerningly," said Dr. Mark Litwin and Dr. David Miller of the University of California, Los Angeles, in an accompanying commentary.

Until the results are confirmed or refuted by randomized control trials, "physicians should apply these provocative findings judiciously and continue their concerted efforts to help patients make informed treatment decisions based not only on survival predictions but also on health status, functional concerns, and most importantly — personal preference," they wrote.