Wednesday, April 28, 2010 (Last Updated: 04/29/2010)
WEDNESDAY, April 28 (HealthDay News) -- As has been reported previously, in men with elevated prostate-specific antigen (PSA), a panel of four kallikrein forms in serum -- total, free and intact PSA, and kallikrein-related peptidase 2 (hK2) -- may predict the result of biopsy and help reduce unnecessary biopsy rates, according to a replication study published online April 26 in the Journal of Clinical Oncology.
Building on previous research, Andrew Vickers, Ph.D., of the Memorial Sloan-Kettering Cancer Center in New York City, and colleagues studied 2,914 previously unscreened men undergoing biopsy indicated by a PSA of at least 3 ng/mL, including 807 (28 percent) who were diagnosed with prostate cancer, and compared the levels of kallikrein markers with biopsy outcome.
The researchers found that the addition of free and intact PSA and hK2 to a model containing total PSA and age was associated with an improved area under the curve of 0.64 to 0.76 for models without digital rectal examination results and 0.70 to 0.78 for models with digital rectal examination. In every 1,000 men with elevated PSA, they calculated that use of the panel would result in 513 fewer biopsies, and would miss 54 of 177 low-grade cancers and 12 of 100 high-grade cancers.
"While decreasing unnecessary prostate biopsies is beneficial, the study by Vickers and colleagues does not address the fundamental questions underlying the use of PSA as a screening test for prostate cancer," state the authors of an accompanying editorial. "The issues of overdiagnosis and overtreatment of prostate cancer are unlikely to be addressed by refinements in PSA testing. Identification of serum or tissue biomarkers that identify aggressive prostate cancer is needed. Without development of tests better than PSA, clinicians and patients will remain uncertain of how to deal with a prostate cancer diagnosis."
One author disclosed holding patents for free PSA and hK2 assays, and he and another author disclosed being co-inventors on a patent application for intact/nicked PSA assays.
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