© 2005 Oxford University Press
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In Brief
Study Finds No Best PSA Value for Decision to Biopsy
For the popular prostate cancer screening test that measures prostate-specific antigen (PSA), no specific value exists that is sensitive enough to detect cancer cases but not yield a high rate of false positives, according to a new study published in the July 6 issue of the Journal of the American Medical Association.
Researchers used data from the placebo group of the Prostate Cancer Prevention Trial (PCPT), in which 18,882 men over the age of 55 were randomly assigned to receive either finasteride or a placebo, to determine the relationship between PSA value and prostate cancer risk. They looked at PSA levels for 8,575 men in the placebo group and modeled the effect of various PSA cutoff points.
They found that using the value of 4.1 ng/mL as the cutoff point to flag the need for a prostate biopsy resulted in the detection of only 20.5% of cancer cases. Moreover, it produced a 6.2% false-positive rate. In trying to improve the rate of detection, the researchers then modeled the use of a PSA value of 1.1 ng/mL. Use of this value successfully detected 83.4% of cancer cases but subjected 61.1% of those flagged to an unnecessary prostate biopsy.
The authors tried several other possible PSA values, but each involved a trade-off between sensitivity/successful detection and false-positive rates. They conclude that no single value can predict cancer risk. Instead, they suggest a continuum of prostate cancer risk across all values of PSA.
Fear of Lawsuits May Affect Radiology Practices
Fearing medical malpractice lawsuits, some doctors may be performing unnecessary breast biopsies and mammograms on their patients, according to a study in the July issue of the journal Radiology.
A failure or delay in diagnosing breast cancer represents the most common and second most expensive medical malpractice claim. Joann Elmore, M.D., M.P.H., of the University of Washington, and colleagues studied the actions and perceptions of 124 radiologists who face these issues.
They found that more than half of the surveyed radiologists reported a prior malpractice claim. Moreover, more than three-quarters of them expressed concern about the impact of the claims on their practices—about 60% admitted that they had increased their number of recommendations for breast biopsies, and more than 70% had increased their recommendations for diagnostic mammography or ultrasound due to fears of lawsuits.
The authors suggest that many women may be subjected to unnecessary expensive and sometimes painful follow-up evaluations or treatments for non–life threatening breast abnormalities because of the fear-induced recommendations.
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