What are some of the limitations of the PSA test?

* Detecting tumors does not always mean saving lives: When used in screening, the PSA test can detect small tumors. However, finding a small tumor does not necessarily reduce a man's chances of dying from prostate cancer. PSA testing may identify very slow-growing tumors that are unlikely to threaten a man's life. Also, PSA testing may not help a man with a fast-growing or aggressive cancer that has already spread to other parts of his body before being detected.

* False-positive tests: False-positive test results (also called false positives) occur when the PSA level is elevated but no cancer is actually present. False positives may lead to additional medical procedures that have potential risks and significant financial costs and can create anxiety for the patient and his family. Most men with an elevated PSA test result turn out not to have cancer; only 25 to 35 percent of men who have a biopsy due to an elevated PSA level actually have prostate cancer (3).

* False-negative tests: False-negative test results (also called false negatives) occur when the PSA level is in the normal range even though prostate cancer is actually present. Most prostate cancers are slow-growing and may exist for decades before they are large enough to cause symptoms. Subsequent PSA tests may indicate a problem before the disease progresses significantly.

PSA Velocity's Clinical Usefulness Remains Unclear

ScienceDaily (Oct. 10, 2007) — Some studies have suggested that the rate of change of prostate-specific antigen (PSA) levels may correspond with prostate cancer survival. But this does not necessarily mean that PSA velocity will be valuable as a prostate cancer screening tool, according to a commentary published online October 9 in the Journal of the National Cancer Institute.

PSA velocity has been the subject of much research and debate since the beginning of the PSA screening era. Initially, PSA velocity was proposed for use in men with moderately elevated PSA levels in order to decrease the number of unnecessary biopsies. But often PSA velocity is being used in men with low PSA levels, effectively increasing the number of men who are referred to have a biopsy.

Ruth Etzioni, Ph.D., of the Fred Hutchison Cancer Research Center in Seattle and colleagues reviewed several recent articles on PSA velocity. They point out in their commentary the important differences between studies of PSA velocity in the cancer screening setting and studies of PSA velocity and prostate cancer progression after diagnosis. These differences lead them to question whether PSA velocity is useful for early detection of prostate cancer.

No studies to date have addressed the costs and benefits of using PSA velocity for prostate cancer screening. "One of the main goals of this commentary has been to reconcile some of the inconsistencies across studies by highlighting features of study design and potential sources of bias that might explain why different types of studies have produced differing results," the authors write.