"How sweet it is!"
Some of the improvement in prostate cancer survival rates over the past decade may be due to a shift in the classification of prostate tumors rather than to an actual improvement in outcomes, according to an article in the September 7 issue of the Journal of the National Cancer Institute.  Prostate cancers are assigned a score called a Gleason score that ranges from 2 to 10, based on the pathologist's estimation of the likelihood that the cancer cells will spread. Twenty years ago, doctors routinely labeled newly diagnosed prostate tumors with relatively low Gleason scores of 2 to 5, indicating a less dangerous cancer.
Today, scores this low are rarely encountered, even though there has been no change in the Gleason scoring system itself in the last decade. In addition, there have been several reports of improvements in 5-year and 10-year survival in prostate cancer based on Gleason score.
Truth in Numbers?To determine whether these improvements in survival are true improvements or the result of a changes in the way cancers are assigned Gleason scores, Peter C. Albertsen, M.D., of the University of Connecticut Health Center in Farmington, and colleagues collected medical records from 1,858 men diagnosed with prostate cancer between 1990 and 1992. The study found that about 55% of the 1,858 specimens received higher scores than the original assignments. The scores increased from an average of 5.95 for the original readings to an average of 6.8 by contemporary standards. In addition, two other pathologists reviewed samples of the slides and also arrived at higher scores than the original readings. The authors suggest that perhaps "pathologists are more hesitant to assign low Gleason scores to contemporary prostate needle biopsy specimens because these scores are frequently upgraded" after reviewing the whole tumor after it has been surgically removed. The authors also suggest that with more tumors labeled with higher Gleason scores than a decade ago, many low-grade tumors are being labeled as more dangerous than they actually are. This re-labeling could skew mortality and survival rates for prostate cancer patients because those higher score categories would include patients with less aggressive forms of the disease. This statistical artifact is known as the Will Rogers phenomenon, based on a Will Rogers joke: "When the Okies moved to California, the IQ of both states went up." The Will Rogers phenomenon of prostate cancer presents a situation "where all the biopsies are necessary and all cancers require treatment, as all have Gleason scores above 5," write Ian M. Thompson, M.D., of the University of Texas Health Science Center in San Antonio, and colleagues in an accompanying editorial. Referring to the phenomenon as "grade inflation," they express concern that score inflation "is a component of the more insidious phenomena of overdetection and overtreatment of prostate cancer." They point out that about 75% of U.S. men have had a PSA test, and more than 17% will be diagnosed with prostate cancer during their lifetime. However, there is only a 3% to 4% lifetime risk of prostate cancer death. Jim Shaw
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