A study of the new five tiered prostate cancer Gleason grading system in a nationwide population cohort in Sweden

Recommendations by the International Society of Urologic Pathology (ISUP) and 2016 World Health Organization (WHO) blue book propose the use of a five-tiered prostate cancer (PCa) grading system (1,2). The five Gleason grade groupings (GGGs) ranging from 1 to 5 are defined as Gleason scores 6, 3+4, 4+3, 8, and >8, respectively (2).This new grading system beginning with grade group 1 has the potential benefit of reducing anxiety in patients and may contribute to a decrease in the overtreatment of low risk PCa detected by prostate specific antigen (PSA) screening (3). The new GGGs (2,3) has not been validated in a population-based setting before the study by Loeb et al. (4). In their study, the authors examined the performance of the new GGGs in men with PCa from a nationwide population-based cohort in Sweden. The authors studied the newly proposed GGGs in 4,325 men undergoing radical prostatectomy (RP) and 1,555 treated with radiation therapy in the national PCa register of Sweden with a mean follow-up of 4.6 years. They showed that the new GGGs was able to predict biochemical recurrence (BCR) after RP and radiation therapy with same accuracy as the previous Gleason classifications, but could potentially avoid overtreatment of low-risk PCa. We eagerly await further results from this group to confirm the prognostic accuracy of the GGGs with longer term oncologic endpoints, and assessment of GGGs in a prospective and the multi-center setting.