PURPOSE: We evaluated the detection rate of prostate cancer in men with suspicious
digital rectal examination findings and serum prostate specific antigen (PSA) 4 ng./ml. or
less. We also evaluated the stage and grade of cancers detected.
MATERIALS AND METHODS: We screened 22,513 community volunteers by PSA testing and
digital rectal examination at 6-month intervals. Biopsy was recommended when either test was
suspicious for cancer. In the subset of 2,703 white and black men in whom PSA was 4 ng./ml.
or less and digital rectal examination was suspicious for prostate cancer we compared
compliance with biopsy recommendations, cancer detection rates, and stage and grade of
cancers detected. We then correlated these results with patient age, race and serum PSA
concentration. We performed multivariate logistic regression analysis to predict cancer based
on clinical characteristics, and evaluated the positive predictive value of digital rectal
examination for detecting cancer as stratified by race and PSA.
RESULTS: Of the men 70% underwent biopsy with no difference in compliance according to
age, race or PSA level. The 13% cancer detection rate correlated with age, race and PSA
(p <0.003). The positive predictive value of a suspicious digital rectal examination was 5,
14 and 30% in men with PSA 0 to 1.0, 1.1 to 2.5 and 2.6 to 4.0 ng./ml., respectively. All
cancers were clinically localized. Of the 72% of cases that were surgically staged 82% were
organ confined and 78% were moderately differentiated.
CONCLUSIONS: The positive predictive value of suspicious digital rectal examination was
appreciable in men with low serum PSA. The majority of cancer cases detected by digital
rectal examination had features of clinically important and potentially curable disease.
