PSA Testing Interval Reduction In Screening Intervals: Data From The Prostate, Lung, Colorectal And Ovarian Cancer (PLCO) Screening Trial

Reviewer: Roberto Santiago, MD
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: May 19, 2002

Presenter: E. D Crawford
Presenter's Affiliation: Univ of Colorado Health Sciences Ctr, Denver, CO
Type of Session: Plenary

Background

Prostate cancer is the most commonly diagnosed malignancy in males and the second leading cause of cancer mortality in males
The prostate, lung, colorectal (PLCO) trial is a large, controlled randomized trial evaluating cancer screening versus usual medical care in subjects between the ages of 55 and 74 years that has recruited over 154,000 men and women
Among the goals in the male cohort is the evaluation of the pattern of PSA change over 5 years in men with an initial normal PSA to examine alternative screening schedules

Materials and Methods

In the screening arm of the trial, the changes in PSA over 5 years was evaluated in 27,863 men who had baseline PSA levels of <4 ng/ml and at least one subsequent PSA exam
PSA was yearly assessed by the Hybritech method for 6 years
Screening digital rectal examination was performed at the first 4 yearly visits
The cumulative probability of converting to PSA >= 4 at years 1 through 5 post baseline was estimated (independent of baseline digital rectal examination)
White men constituted 86.1% of the cohort

Results

For men with PSA under 1ng/ml at baseline, 98.4% would still have a PSA < 4 ng/ml after 5 subsequent years of annual screening
For men with a baseline PSA of 1-2 ng/ml, 97.5% would have a PSA < 4 ng/ml after 2 years of annual screening
For men with a baseline PSA of 2-3 ng/ml there is a 34.6% probability of converting to a positive PSA (> 4 ng/ml) after 5 years of annual screening
For those with a baseline between 3 and 4 ng/ml the likelihood of having a PSA > 4 ng/ml 5 years after is 83%

Author's Conclusions

If a PSA screening strategy that tests every 5 years for men with PSA below 1ng/ml and every 2 years for men with PSA 1-2 ng/ml is implemented a 55% reduction (15.7 million fewer tests) in the number of PSA tests would be achieved
This would only result in a small proportion 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

Clinical/Scientific Implications

The study did not stratified by age
Since controversy exists on whether early identification of an abnormal PSA improves the clinical outcome the impact of this study will depend to a certain degree on the results of prospective randomized studies evaluating prostate cancer mortality among patients undergoing cancer screening versus usual medical care

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