Validation of a Contemporary Five-tiered Gleason Grade Grouping Using Population-based Data.

This population-based study assesses whether a proposed five-tiered Gleason grade grouping (GGG) system predicts prostate cancer-specific mortality (PCSM). Using the Surveillance, Epidemiology, and End Results (SEER) database, we identified 331320 prostate cancer patients who had primary and secondary Gleason patterns diagnosed between January 2006 and December 2012. We used the Fine and Gray proportional hazards model for subdistributions and the corresponding cumulative incidence to quantify the risk of PCSM. We found that the risk of PCSM approximately doubled with each GGG increase. Among men who underwent radical prostatectomy and using GGG1 (Gleason score ≤6) as the reference group, the adjusted hazard ratio for PCSM was 1.13 (95% confidence interval [CI] 0.83-1.54) for GGG2, 1.87 (95% CI 1.33-2.65) for GGG3, 5.03 (95% CI 3.59-7.06) for GGG4, and 10.92 (CI 8.03-14.84) for GGG5. Similar patterns were observed regardless of the type of primary cancer treatment received or clinical stage. In summary, our study, with large, racially diverse populations that reflect real world experiences, demonstrates that the new five-tiered GGG system predicts PCSM well regardless of treatment received or clinical stage at diagnosis. PATIENT SUMMARY In this report we examined prostate cancer mortality using the new five-tiered cancer grading system using data for a large US population. We found that the new five-tiered cancer grading system can predict prostate cancer-specific mortality well, regardless of the type of primary cancer treatment and clinical stage. We conclude that this new five-tiered cancer grading system is useful in guiding treatment decisions.