Release Date: 07/31/2008
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Lahey Clinic prostate study shows current cancer grading system flawed
BURLINGTON, MA—Physicians from Lahey Clinic, in the August issue of European Urology, have published a significant research study that questions the accuracy of the time-honored prostate cancer grading system, known as the Gleason score, used both in presurgical biopsy and prostatectomy (removal of the prostate) specimens.
The Gleason score ranges from 2-10, with the lowest scores believed to be less aggressive cancers. Because the study demonstrates the Gleason score is not always accurate, a lower Gleason score taken on biopsy, for example, can mislead physicians and patients into believing there is no aggressive cancer present. Treatments may then be delayed because they opt to monitor the cancer, better known as “watchful waiting.”
Findings demonstrate a universal inaccuracy of the biopsy grade to predict prostatectomy grade. The biopsy grade had an overall accuracy of only 63 percent, according to the study. On prostatectomy sample, 30 percent of patients were found to actually have higher-grade (upgraded) cancer, while 7 percent had lower-grade (downgraded) cancer.
High-grade cancer on the Gleason score biopsy was the least accurate because the cancer was downgraded in half of all patients. And of the patients with high-grade cancer on prostatectomy Gleason, about 67 percent had either low- or moderate-grade cancers on biopsies. Of the patients with low-grade prostate cancer on biopsy, 53 percent had either a moderate or high-grade cancer on prostatectomy specimen.
In preparing their study, the authors compared biopsy and prostatectomy grades at Lahey Clinic for nearly 3,000 patients from 1982 through 2007. Then to evaluate the accuracy on the international scale, they conducted a meta-analysis that included the Lahey Clinic patients and results from 16 studies involving six countries and comprising 14,000 total patients. (A meta-analysis is a set of statistical methods for combining information from existing studies to derive an overall estimate.)
The Lahey study is the largest single institutional database and the largest international database comparing biopsy and prostatectomy Gleason grades.
Based on the study, patients and physicians need to be aware of significant upgrading for low-grade disease and downgrading for high-grade disease. The authors do not advocate “watchful waiting” as a strategy, which can delay treatment of advancing cancers. Future research on biopsy techniques and tumor markers are recommended, along with improvements in grading systems.
John A. Libertino, MD, director and chair of the Lahey Clinic Institute of Urology, has an international reputation for excellence in urologic surgeries and has pioneered complex urologic surgical techniques. He co-authored the study, along with nine other physicians, two who are from Tufts Medical Center.
About Lahey Clinic
Lahey Clinic, a physician-led, nonprofit group practice, is world-renowned for innovative technology, pioneering medical treatment, and leading-edge research. A teaching hospital of Tufts University School of Medicine, the Clinic provides quality health care in virtually every specialty and subspecialty, from primary care to cancer diagnosis and treatment to kidney and liver transplantation.