News Release
September 6, 2005
Embargoed until Tuesday, September 6, 4 p.m. EST
Contact: Carolyn Pennington, 860-679-4864
e-mail:
cpennington@uchc.edu
Improvements in Prostate Cancer Survival Rates May Be Result of Classification Change
FARMINGTON, CONN. – 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 an actual improvement in outcomes, according to researchers at the University of Connecticut Health Center. The findings are published 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, depending on how likely a pathologist thinks the cancer cells will spread. Twenty years ago, doctors routinely labeled newly diagnosed prostate tumors with a relatively low Gleason score 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 in the last decade. In addition, there have been several reports of improvements in 5-year and 10-year survival rates in prostate cancer patients based on Gleason scores.
To determine whether these improvements in survival are true improvements or the result of changes in the way cancers are assigned Gleason scores, Peter Albertsen, M.D., professor and chief of urology at the UConn Health Center, and colleagues, collected medical records from 1,858 men diagnosed with prostate cancer between 1990 and 1992. Slides of the diagnostic prostate tissue taken from these men at the time of their diagnosis, as well as the original Gleason score assignments, were used. An experienced pathologist, with no knowledge of the original numbers, examined the slides and calculated Gleason scores according to contemporary standards.
The study found that about 55 percent of the 1,858 specimens received higher scores than the original readings. On average, the new scores were 0.85 points higher than the original scores, increasing from an average of 5.95 for the original readings to an average of 6.8 by current standards. Two other pathologists also reviewed samples of the slides and also arrived at higher scores than the original readings.
Dr. Albertsen suggests that perhaps pathologists now are more hesitant to assign low Gleason scores to prostate needle biopsy specimens because these scores are frequently upgraded after examining the whole tumor following surgical removal.
According to Dr. Albertsen, there is also the possibility that with more tumors labeled with higher Gleason scores, many low-grade tumors may be labeled as more dangerous than they actually are. This re-labeling could skew mortality and survival rates for prostate cancer patients because those score categories would include patients with weaker forms of the disease.
For example, the study found that current prostate cancer mortality rates appeared to be 28 percent lower than standardized historical rates, even though the overall number of deaths remained the same. “The reclassification of prostate tumors may be producing a false sense of therapeutic accomplishment,” says Dr. Albertsen.
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