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Recommendations for timing of PSA
screening for PC presented at American Society of Clinical Oncology, May
2002. (December 2002)
Efficiency in PSA testing: Dr. David
Crawford (Plenary Session, ASCO,2002,Abstract #4) presented data to
improve the efficiency and economy of PSA testing. He reported early
analysis of rate of rise in the PSA of 27,863 men (age 55-74) over a
five-year period of observation studied in the Prostate, Colorectal, Lung,
and Ovary Screening Study. Baseline PSAs and DREs were performed and
reevaluated yearly for five years, although not all men had yearly
testing. All men had PSA values below 4 ng/mL. The study goal was to learn
how many men and at what rate would they "convert" to a PSA greater than
4. The findings: If the PSA was <1 at baseline the risk of a rise of PSA
to >4 at five years was 1.6%; for PSA between 1-2 risk was 7.6%; PSA 2-3
risk was 34.6%, PSA 3-4 risk was 83%. Stated differently, the findings
show that a man with a <1 PSA at baseline had a 98.6% likelihood of being
below 4 in five years; and a man with PSA between 1-2 had a 98.8%
likelihood of being below 4 after 2 years. This data led to a preliminary
suggestion for testing frequency: baseline <1 test every five years;
baseline 1-1.9 test every two years; and baseline >2 test annually.
This is useful data. However, applying the full context of our current
knowledge we know that among men within the PSA range of 2.5 to 4 about
25%-30% harbor significant cancers. As yet, the study data analysis does
not include reference to the velocity of PSA rise in the individual
converters, although the rate of rise of a cohort can be surmised. For
example, take the group with baseline PSA 2-3. The yearly conversion rate
is 6.3% by one year, 12.8% by two years, 19.4% by three, 30.4% by four,
and at five years, 34.6% - hence, yearly testing for this group. If Dr.
Crawford's recommendations were followed 55% fewer PSA's would be run and
an estimated savings would accrue of $500 million to a $1 billion. This
study offers relevant guidance until advances in science helps us take a
more positive step in the area of diagnostics.
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