Adding radiotherapy to hormone drugs for prostate cancer patients significantly improves survival compared with hormone treatment alone, and the combination could save many lives if it were made standard practice, scientists said Thursday.

In a study of men with prostate cancer -- the second most common form of cancer among men worldwide -- researchers found that 74 percent of those given radiotherapy plus hormone treatment were still alive after seven years.

This compared with 66 percent who got hormone drugs but did not receive radiotherapy, the researchers said.

"The results of this trial are extremely encouraging," said Matthew Sydes, senior scientist at Britain's Medical Research Council's Clinical Trials Unit, which helped conduct the study.

He said the additional side-effects of radiotherapy are "minimal," suggesting doctors could be confident in recommending the combination treatment for their patients.

After lung cancer, prostate cancer is the second most common cancer in men worldwide and kills an estimated 255,000 men a year.

This study, conducted between 1995 and 2005, involved more than 1,200, men mostly from Britain and Canada, who had been diagnosed with locally advanced prostate cancer which had grown outside the surface of the prostate but had not spread further.

Half the men were treated with hormone drugs called androgen deprivation therapy, a standard form of treatment in this type of cancer, and the rest were treated with the same hormone therapy plus a course of radiotherapy.

The results were published in the Lancet medical journal.

"The trial has shown that radiotherapy is extremely worthwhile for patients with prostate cancer that is locally advanced," said Malcolm Mason from Cardiff University, who worked on the study with the trial's lead researcher, Padraig Warde of Toronto's University Health Network.

"The next stage will be to ensure that the results...are implemented into treatment recommendations as quickly as possible."