Most men over age 75 can safely discontinue screening for prostate cancer with the PSA blood test, although such screening may still benefit some older men, U.S. researchers said on Friday.

Use of the prostate-specific antigen blood test to screen for prostate cancer in elderly men has been controversial. A panel of experts called the U.S. Preventive Services Task Force last year urged doctors to stop screening men 75 and older.

The new findings involved 849 U.S. men taking part in a study of aging run by the National Institutes of Health.

For men over 75, not one died of prostate cancer if they had a PSA reading below 3 nanograms per milliliter. That represents at least two thirds of the population.

Because PSA screening has led to a big increase in prostate cancer diagnoses, some experts believe many men with tumors that pose little threat are getting treatment such as surgery and radiation that may be unnecessary.