PSA testing interval reduction in screening intervals: data from the prostate, lung, colorectal and ovarian cancer (PLCO) screening trial.

E. D Crawford, David Chia, Gerld L Andriole, Douglas Redding, Edward P Gelmann, John K Gohagan, Paul Pinsky, Richard B Hayes, David L Levin, Richard M Fagerstrom, Barnett S Kramer, Univ of Colorado Health Sciences Ctr, Denver, CO; University of California at Los Angeles, Los Angeles, CA; Washington University School of Medicine, St Louis, MO; Marshfield Clinic and Medical Center, Marshfield, WI; Georgetown University Medical Center, Washington, DC; NIH/NCI, Division of Cancer Prevention, Bethesda, MD; NIH/NCI, Office of Medical Applications of Research, Bethesda, MD.

Purpose: To determine the pattern of prostate specific antigen (PSA) change over 5 years in men with an initial normal PSA. Method: The prostate, lung, colorectal (PLCO) trial is a large, controlled trial that has recruited over 154,000 men and women, ages 55-74, and randomized them to a screening or usual care arm. For men, PSA is assessed (Hybritech method) at each of 6 yearly screening rounds; digital rectal examination (DRE) is carried out at the first four annual exams. We evaluated changes in (total) PSA over 5 years among 27,863 men in the screening arm of the trial who had baseline PSA levels of <4 ng/ml and at least one subsequent PSA exam. A statistical model was used to estimate the cumulative probability of converting to PSA>= 4 at years 1 through 5 post baseline. PSA conversion probabilities were independent of baseline DRE status. Results: The results are illustrated in the table below. Conclusions: This study has found that 98.6% of men with PSA under 1ng/ml at baseline would remain negative (i.e., PSA < 4 ng/ml) after 4 subsequent years of annual PSA testing, and that 98.8% of men with a baseline PSA of 1-2 ng/ml would have a negative PSA test the following year. A strategy of PSA screening every 5 years for men with PSA below 1ng/ml and every 2 years for men with PSA in the 1-2 ng/ml range would produce a 55% reduction in the number of PSA tests, but result in only a small percentage of men missing an earlier potentially positive test. The estimated cost savings of this strategy is on the order of a billion dollars per year.

PSA at Year 0

0-1

1-2

2-3

3-4

Estimated % Converting to PSA 4 ng/ml (95% CI)

       

Year 1

0.25 (0.21-0.32)

1.2 (1.0-1.3)

6.3 (5.7-6.9)

24 (22-26)

Year 2

0.53 (0.45-0.66)

2.5 (2.2-2.8)

12.8 (11.8-14.3)

44 (42-47)

Year 3

0.83 (0.70-1.0)

3.9 (3.5-4.4)

19.4 (17.9-20.9)

60 (58-63)

Year 4

1.4 (1.2-1.8)

6.6 (4.8-6.0)

30.4 (27.9-32.9)

77 (74-80)

Year 5

1.6 (1.4-2.0)

7.6 (6.8-8.4)

34.6 (32.1-37.1)

83 (80-85)