Comparison of Japanese General Rules of Prostatic Cancer and Gleason grading system

Abstract Background: We compared the prognostic efficacy between the Japanese General Rules of Prostatic Cancer (JGRPC) and the Gleason grading system (GGS) by applying them to a single set of patients and assessing the survival outcome.Methods: One hundred and seventy‐six patients with previously untreated prostate cancer were studied. One experienced Japanese pathologist graded the slides with JGRPC. Another experienced American pathologist graded the same slides with the Gleason grading system. The JGRPC grades were correlated with the Gleason scores (GS) grouped into three (GS 2–4, 5–7 and 8–10) or four (GS 2–4, 5–6, 7 and 8–10) tiers.Results: The highest cancer death rates were seen in the higher grade groups in both systems. Comparison of JGRPC grade and three‐tiered grouping of the GS showed identical grades in 81 of 176 cases (46.0%). The overall kappa value of agreement was only 0.151. The 96 cases of JGRPC moderately differentiated carcinoma group contained two nearly equal‐sized groups by the Gleason grading system, those with GS 5–7 (47cases) and GS 8–10 (49 cases). There was a significant difference in survival rate between the GS 5–7 and GS 8–10 groups. No significant differences were noted in the reverse analysis of survival by JGRPC groups within patients with the same GS three‐tiered groups. Similar trends were seen when JGRPC was compared with the four‐tiered grouping of the GS.Conclusion: Both JGRPC and the Gleason grading system are useful in estimating the prognosis of prostate cancer, but only a mild correlation was found between the two systems. The Gleason grading system may provide more prognostic information than JGRPC in the moderately differentiated group.