Impact on the Clinical Outcome of Prostate Cancer by the 2005 International Society of Urological Pathology Modified Gleason Grading System

The 2005 International Society of Urological Pathology (ISUP) Consensus Conference modified the Gleason grading system for prostate cancer. In the modified criteria, ill-defined glands with poorly formed lumina and large cribriform glands with smooth borders, classically described as Gleason pattern 3 adenocarcinoma, were redefined as Gleason pattern 4. To evaluate the clinical outcome of patients upgraded by the ISUP criteria, the histologic slides of 1240 consecutive radical prostatectomy specimens at a single institution were reviewed, and each case of adenocarcinoma was graded on the basis of the original and modified Gleason criteria. A total of 806 patients with prostate cancer of classical Gleason score 3 + 3 = 6 or 3 + 4 = 7 and modified Gleason score 6 to 8 were analyzed with a median overall follow-up of 12.6 years. In the study population, 34% of patients with classical Gleason score 3 + 3 = 6 prostate cancer were upgraded to modified Gleason score 7 or 8 by the ISUP criteria. Compared to patients with modified Gleason score 3 + 3 = 6 and patients with classical Gleason score 3 + 4 = 7, the upgraded patients were at intermediate risk for biochemical progression (paired log-rank P <= 0.003) and metastasis (paired log-rank P <= 0.04) after radical prostatectomy. The hazard ratio for upgrading was 1.60 (95% confidence interval, 1.09-2.35, P = 0.02) for biochemical recurrence and 5.02 (95% confidence interval, 1.77-14.2, P = 0.003) for metastasis. These results validate the prognostic value of the modified Gleason grading system and suggest that the recognition of an intermediate-risk histological pattern may be useful in the prognosis of patients with prostate cancer.