Less Frequent PSA Testing May Be Possible
ABSTRACT & COMMENTARY
Synopsis: If the initial PSA is less than 2 ng/mL, a two-year testing interval may be possible.
Source: Carter HB, et al. JAMA 1997;277:1456-1460.
Despite the controversy surrounding the benefits of early detection of prostate cancer, PSA testing is widely performed. Common thresholds for further investigation are either a level of 4 ng/mL or an age-specific nomogram beginning at 2.5 ng/mL in younger men to 6.5 in men over 70. All authorities currently suggest annual testing.
Carter and colleagues from Johns Hopkins have addressed the question of whether men with low PSA levels can have less frequent testing. Using data collected in the Baltimore Longitudinal Study of Aging, frozen serum samples of 40 men who developed prostate cancer, 272 men who did not develop cancer, and the correlation of PSA with nonpalpable cancers of 389 different men were assessed.
Since the authors knew which men had prostate cancer and if it were "curable" based on surgical stage, they were able to assess different PSA cutoff levels and different durations of testing. If a PSA of 5 ng/mL was used, no men with an initial PSA of less than 2.0 ng/mL developed prostate cancer in four years. Using a threshold of 4 ng/mL, only one man developed prostate cancer using a two-year testing interval.
COMMENT BY BRUCE E. HILLNER, MD
This provocative study confirms my intuition about the natural history of prostate cancers. Estimates are that 50-70% of men between ages 50 and 70 will have PSA below the 2 ng/mL threshold. The major limitation of this study is the need for validation in another population. If confirmed, substantial cost savings and reduced patient anxiety should ensue.
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