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Objective: To assess the impact of the 2005 modification of the Gleason classification on risk of biochemical recurrence (BCR) after radical prostatectomy (RP).

Patients and Methods: In the Prostate Cancer data Base Sweden (PCBaSe), 2,574 men assessed with the original Gleason classification and 1,890 men assessed with the modified Gleason classification, diagnosed between 2003 and 2007, underwent primary RP. Histopathology was reported according to the Gleason Grading Groups (GGG): GGG1 = Gleason score (GS) 6, GGG2 = GS 7(3 + 4), GGG3 = GS 7(4 + 3), GGG4 = GS 8 and GGG5 = GS 9–10. Cumulative incidence and multivariable Cox proportional hazards regression models were used to assess difference in BCR.

Results: The cumulative incidence of BCR was lower using the modified compared to the original classification: GGG2 (16% vs. 23%), GGG3 (21% vs. 35%) and GGG4 (18% vs. 34%), respectively. Risk of BCR was lower for modified versus original classification, GGG2 Hazard ratio (HR) 0.66, (95%CI 0.49–0.88), GGG3 HR 0.57 (95%CI 0.38–0.88) and GGG4 HR 0.53 (95%CI 0.29–0.94).

Conclusion: Due to grade migration following the 2005 Gleason modification, outcome after RP are more favourable. Consequently, outcomes from historical studies cannot directly be applied to a contemporary setting.