Early detection of prostate cancer .1. Prior probability and effectiveness of tests

Purpose: To estimate the prevalence of clinically important prostate cancer and to evaluate the effectiveness of digital rectal examination and measurement of prostate-specific antigen (PSA) in early detection of prostate cancer. Data Sources: Relevant studies were identified from a structured MEDLINE search (1966 to 1995), reviews, bibliographies of retrieved articles, author files, and abstracts. Study Selection: Articles selected for analysis of test effectiveness were prospective cohort studies of early detection that did not have obvious selection bias. Data Extraction: Likelihood ratios for digital rectal examination and PSA measurement were estimated from studies that specified the age distribution of participants. Data Synthesis: In patients who have abnormalities on digital rectal examination, the risk for a large, intracapsular tumor is increased twofold but the risk for extracapsular disease is increased threefold to ninefold. An elevation in PSA level greater than 4 ng/mL increases the odds of intracapsular tumors by as much as threefold and the odds of extracapsular tumors by threefold to fivefold, For studies in which biopsies were done if results of either test were abnormal, 18% to 26% of screened patients had suspicious results, cancer detection rates were approximately 4%, and the positive predictive Value of the tests combined was 15% to 21%. Men who have lower urinary tract symptoms that are consistent with benign prostatic hyperplasia are not more likely to harbor prostate cancer; the specificity of PSA measurement is considerably lower among these men. Conclusions: Larger-volume tumors of the prostate are common among older men. Available tests for the early detection of cancer have limited specificity, which necessitates a relatively high biopsy rate. The positive predictive value of combined digital rectal examination and PSA measurement has been defined, but the negative predictive value is less clear. Measurement of PSA is the most sensitive noninvasive test for prostate cancer, However, digital rectal examination detects cancer that would otherwise be missed by PSA measurement.