The consensus panel was convened in 2014 by ISUP and included 65 PCa pathology experts as well as 17 clinicians, including urologists, radiation oncologists, and medical oncologists from 19 countries.
The new grading system and terminology of grade groups 1 through 5 have been accepted by the World Health Organization for the 2016 edition of Pathology and Genetics: Tumours of the Urinary System and Male Genital Organs.
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As for how quickly the new system will be adopted by US clinicians, Dr Epstein said that this depends largely on its adoption by the College of American Pathologists checklists, to which every medical institution adheres.
This often follows what the Union for International Cancer Control (UICC) and the American Joint Committee on Cancer (AJCC) do with respect to the Tumor Node Metastasis Classification of Malignant Tumors, which both groups maintain.
“The new grading system has some significant advantages over the Gleason grading system,” said David F. Penson, MD, chair of the Department of Urologic Surgery and director of the Center for Surgical Quality and Outcomes Research at Vanderbilt University Medical Center in Nashville, TN. He also mentioned how the Gleason system can mislead patients into believing their prognosis is worse than it is.
“Resetting the grading system so the lowest risk cancers are a grade group 1 will be very helpful for patient counseling and will aid in the further uptake of active surveillance in appropriate men with low-risk disease.”
The differentiation between Gleason 3 + 4 and 4 + 3 as grade groups 2 and 3 is also an important advance that will improve patient education and future studies of PCa, Dr Penson said. “Specifically, many administrative and institutional databases fail to differentiate between 3 + 4 and 4 + 3 disease, reporting both as Gleason score 7, he said.
“This is probably not the optimal approach given that studies show that there are differences in outcomes between the 2 groups.”
Although the proposed grade group system is an advance, some questions still remain. The validation data presented by Dr Epstein uses biochemical recurrence-free survival as the endpoint.
“As we know, not all biochemical recurrences result in a clinical event such as metastasis or death and, of course, the definition of a biochemical recurrence differs between surgery and radiation. It’s also not entirely clear to me how patients who have a tertiary Gleason pattern on prostatectomy will be graded in the new system,” he said.
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Given these and other remaining questions, further study of the new system is needed.
“That being said, however, it is definitely time for us to take a critical look at the Gleason grading system and develop better approaches to pathologic grading of prostate cancer,” Dr Penson said. “Gleason developed his scoring system roughly 50 years ago. Our understanding of prostate cancer has obviously advanced exponentially since then. The new grading system is definitely a big step forward in the care of this disease.”
References
- Pierorazio PM, Walsh PC, Partin AW, Epstein JI. Prognostic Gleason grade grouping: data based on the modified Gleason scoring system. BJU Int. 2013;111(5):753-760.
- Epstein JI, Zelefsky MJ, Sjoberg DD, et al. A contemporary prostate cancer grading system: a validated alternative to the Gleason score. Eur Urol. 2016;69(3):428-435.
