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BALTIMORE, Feb. 20 -- PSA testing for prostate cancer can be safely discontinued at age 75 in men who have PSA values less than 3 ng/mL, data from a large cohort study suggest.

No prostate cancer deaths occurred in 75- to 80-year-old men with PSA values below that level, Edward M. Schaeffer, M.D., of Johns Hopkins, and colleagues reported online in the Journal of Urology.

Moreover, the time to death or diagnosis of aggressive prostate cancer was significantly longer in men with PSA values of <3 ng/mL compared with those with values ≥3 ng/mL.

"Men 75 to 80 years old with a prostate specific antigen less than 3 ng/mL are unlikely to die of or experience aggressive prostate cancer during their remaining life, suggesting that prostate specific antigen testing might be safely discontinued for these men," the authors concluded.

The study was first reported at the 2008 meeting of the American Urological Association. (See: PSA Testing Might Not Be Necessary for Older Men)

Older men with low-risk prostate cancer may have an increased risk of unnecessary treatment because of competing causes of death. High rates of PSA screening have been reported in men ages 85 and older, a group for whom treatment of prostate cancer is unlikely to alter mortality, the authors said.

To investigate the potential risks of stopping PSA testing at age 75, the authors reviewed data on 849 men participating in the Baltimore Longitudinal Study on Aging. Median follow-up was 10 years during which the men had a median of four PSA tests.

The study group included 122 men with prostate cancer and 727 men without prostate cancer. The latter group included 185 who had died during follow-up, 24 (3.3%) of whom had prostate cancer diagnosed at autopsy.

Participants ranged in age from 40 to 92.

The median PSA value at first visit was 0.76 ng/mL overall, 1.25 ng/mL in men with prostate cancer, and 0.7 ng/mL in those without prostate cancer (P=0.001).

The median final PSA values were 1.5 ng/mL, 5.1 ng/mL, and 1.23 ng/mL (P=0.001).

Median age at prostate cancer diagnosis was 72.7. Median age at death or censoring was 75.2 overall, 83.1 in men with prostate cancer, and 73.1 in men without prostate cancer (P<0.001).

The authors calculated the probability of developing high-risk prostate cancer in five-year increments, beginning at ages 60 to 65 and stratified by PSA values of <1 ng/mL to >3 ng/mL.

They defined high-risk prostate cancer as death from prostate cancer, a PSA value >20 ng/mL, or a Gleason score of ≥8 at prostate cancer diagnosis.

Of the 122 men with prostate cancer, 18 died of the disease and 17 had high-risk cancer.

In the subgroup of 35 patients, all had one or more PSA values >3 ng/mL during follow-up, compared with none of the 87 patients living with prostate cancer or the 727 prostate cancer-free patients.

"Men of all ages with a prostate specific antigen of 3.0 ng/mL or greater had a continually increasing probability of death from prostate cancer," the authors said.

The researchers acknowledged that their study was limited by the use of frozen sera for PSA assay and the inability to assess the stage or grade of prostate cancer in the diagnosed cases.

Also, they said, "although a majority of deaths occurred at the beginning of the PSA era (early 1990s), the potential impact of treatment on prostate cancer mortality is unknown."

Dr. Schaeffer disclosed a financial relationship with Covidien.

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