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New Prostate Cancer Grading System Validated

A proposed simpler grading system for prostate cancer (PCa) can predict the risk of dying from PCa, according to a new study.

In the new system, PCa patients are placed into 1 of 5 grade groups based on primary and secondary Gleason score (GS) and other criteria, with Grade Group 1 indicating the most favorable prognosis and Grade Group 5 the least favorable. GS 6 cancers (3 + 3) are placed into Grade Group 1 and GS 7 cancers are subdivided into 3 + 4 and 4 + 3 disease. GS 3 + 4 cancers are associated with significantly better prognoses than GS 4 + 3 cancers and are placed into Grade Group 2 and 3, respectively. The new system also subdivides GS 8–10 cancers into GS 8 and GS 9–10 cancers.

In a large population-based study of PCa patients, Grace L. Lu-Yao, PhD, of Thomas Jefferson University in Philadelphia, and colleagues found that the risk of PCa-specific mortality (PCSM) approximately doubled with each Gleason Grade Group increase. The system predicted PCSM regardless of treatment received or clinical stage at diagnosis, the researchers reported online ahead of print in European Urology.

Using the Surveillance, Epidemiology and End Results (SEER) database, Dr Lu-Yao’s team identified 331,320 PCa patients who had primary and secondary Gleason patterns diagnosed during January 2006 to December 2012. The cumulative incidence of 7-year PCSM after RP was 0.43%, 0.48%, 0.80%, 2.13%, and 4.57% for Grade Group 1 to 5, respectively. Among men who underwent radical prostatectomy (RP), those in Grade Group 2 through Grade Group 5 had a 1.13, 1.87, 5.03, and 10.92 times increased risk of PCSM, respectively, compared those in Grade Group 1.

The primary strength of the study was the large population-based sample size with racially diverse populations that reflect real world experiences, Dr Lu-Yao and colleagues stated. Major limitations include short follow up and the lack of PSA data at diagnosis. In addition, the investigators were not able to determine whether patients received active surveillance, watching waiting, androgen-deprivation therapy, or adjuvant therapy.

In a previous study, Misop Han, MD, of Johns Hopkins Medical Institutions in Baltimore, Maryland, demonstrated that the grading system can predict all-cause mortality and PCSM following RP among on men with Gleason score 8–10 disease based on GS at both biopsy and RP. The investigators evaluated the significance of distinguishing GS 8 and GS 9–10 in terms of long-term survival outcomes for both the preoperative setting using biopsy GS and the postoperative setting with RP GS. The study included 721 men with biopsy GS 8–10 and 1047 with RP GS 8–10. Compared with men who had GS 8 disease, men with GS 9–10 disease had later RP year and higher pathologic stage, Dr. Han’s team reported online ahead of print in European Urology. Among men with biopsy GS 8–10, 115 died (82 due to PCa) with a median follow-up of 3 years. Of men with RP GS 8–10, 221 died (151 due to PCa) with median follow-up of 4 years.

For both biopsy and RP GS, men with GS 9–10 disease had a significant 2-fold higher risk of PCa-related death than those with GS 8 disease in multivariable analysis, Dr Han’s group reported. Men with biopsy and RP GS 9–10 disease had a significant 1.9 times and 1.6 times increased risk of all-cause mortality, respectively, compared with men who had biopsy and RP GS 8 disease.

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