Digital rectal examination for detecting prostate cancer at prostate specific antigen levels of 4 ng./ml. or less

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.