The Particulars: Measuring prostate-specific antigen (PSA) has been shown to be an effective way to screen for prostate cancer. However, to prevent a single prostate cancer-related mortality, PSA measurements require that many men be screened, biopsied, and diagnosed.
Data Breakdown: For a study that focused on increasing the specificity of screening for lethal prostate cancer, investigators sought to determine the relationship between four kallikrein markers (kallikrein-related peptidase 2 and total, free, and intact PSA) and long-term risk of metastasis. Kallikrein markers were measured in cryopreserved blood from 1,423 incident prostate cancer cases and 2,345 men with evidence of distant metastasis. Among men with above-average PSA levels, a screening model based on the four kallikrein markers improved the prediction of distant metastasis at 10 to 20 years when compared with using PSA alone. Discrimination increased from 0.77 with PSA alone to 0.88 with the kallikrein markers among men with PSA levels of 2 ng/ml or greater at age 50 and from 0.81 to 0.87 for those with PSA levels of 2 ng/ml or greater at age 60.
Take Home Pearl: Measuring four kallikrein markers appears to improve the specificity of prostate cancer screening among men with modestly elevated PSA levels at age 50 to 60 when compared with measuring PSA only.