The Role of PSA Velocity in the Early Detection of Prostate Cancer
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The controversial decision by the United States Preventive Services Task Force (USPSTF) recommending against screening for prostate cancer with the prostate specific antigen (PSA) test has resulted in confusion for patients and physicians alike.
Historically, urologist referral to discuss the need for a diagnostic prostate biopsy has been based on the use of threshold values (ranging between 3-4ng/ml) to determine an elevated PSA. However, PSA levels change with age, so there is no specific cutoff value that can be universally applied to all men. Further, the PSA test is not specific for prostate cancer, which means that there are many conditions, not all cancerous, that can result in an elevated PSA value. As a result many men undergo unnecessary prostate biopsies for benign conditions such as inflammation or enlargement of the prostate.
Although not a new concept, a recent study has suggested that assessing changes in PSA over time (PSA velocity) may improve the accuracy of aggressive prostate cancer detection when compared to a single measurement of PSA alone1. It has been proposed that a PSA rise of 0.75 ng/ml or greater may be concerning for cancer in patients with a PSA between 4 and 10ng/ml, while a PSA velocity threshold of 0.4ng/ml has been proposed for younger men with baseline levels <4ng/ml.
While thought provoking, the jury is still out, as other investigators have found that the predictive value of PSA velocity may not improve detection compared to PSA alone.
While further research is needed to validate these efforts, alternative uses of the PSA test offer the promise of improving the sensitivity (identifying more aggressive cancers) and specificity (avoiding unnecessary biopsies) of prostate cancer screening. In fact, a recent update to the American Urological Association Prostate Specific Antigen Best Practice Statement recommends that in patients that choose to undergo screening, the decision to proceed to prostate biopsy should be based primarily on PSA and digital rectal exam results, but should take into account multiple factors including free and total PSA, patient age, PSA velocity, PSA density, family history, ethnicity, prior biopsy history, and co-morbidities2.
More simply, this means that the decision to proceed with biopsy can be complex, and should be tailored to each individual following informed discussion between each patient and their urologist. In light of the USPSTF recommendations, new emphasis has been placed on avoiding unnecessary biopsies as well as the over diagnosis and treatment of low risk disease. We are hopeful that in the future discovery of new biomarkers will help more accurately identify men with aggressive cancers early when they are most likely to benefit from treatment. Until then, physicians will continue to rely on various interpretations of the PSA test, including PSA velocity, to guide targeted screening and personalized therapy.
1. Wallner LP, Frencher SK, Hsu JY, Chao CR, Nichol MB, Loo RK, Jacobsen SJ. Changes in serum prostate-specific antigen levels and the identification of prostate cancer in a large managed care population (in press, article first published online January 15th, 2013).
2. Greene KL, Albertsen PC, Babaian RJ, Carter HB, Gann PH, Han M, Kuban DA, Sartor AO, Stanford JL, Zietman A, Carroll P. Prostate specific antigen best practice statement: 2009 update. J Urol. 2013; 189(1 Suppl):S2-S11.