Patients receiving radiation treatment are three times as likely to survive a relapse of prostate cancer than those who have none, a study has found.
Between 15% and 40% of men who undergo surgery for prostate cancer experience a recurrence of their illness within five years.
Whether or not a remedial course of radiotherapy can help them survive longer had been unknown until now.
US researchers, led by Dr Bruce Trock from the Johns Hopkins University School of Medicine in Baltimore, studied 635 men who underwent a radical prostatectomy - removal of the prostate gland - between 1982 and 2004 and later had a relapse.
They were offered either no treatment other than observation, so-called salvage radiotherapy alone, or radiotherapy combined with hormonal therapy.
Over a period of about six years after disease recurrence, 116 men - 18% of the total - died from prostate cancer.
Of these, 89 had received no salvage treatment, 18 had only received radiotherapy, and nine had received radiotherapy plus hormonal therapy, according to the results reported in the Journal of the American Medical Association.
Patients given salvage radiotherapy lived three times longer on average than those offered no salvage treatment.
Whether or not hormone therapy was given in addition to radiotherapy made no significant difference.