Prognostic significance of histologic grading in patients with prostate carcinoma who are assessed by the Gleason and World Health Organization grading systems in needle biopsies obtained prior to radiotherapy.

BACKGROUND

The current study was conducted to evaluate and compare the impact of two major histologic grading systems on failure-free survival in patients with prostate carcinoma who are treated with definitive radiation.

METHODS

Eligible patients for the current study had localized adenocarcinoma of the prostate (T1-4pN0M0, T3/4: 67%, median observation time: 69 months) and were treated with intent-to-cure external radiotherapy between 1989 and 1995. The specimens from 178 patients, obtained by needle biopsies, were reviewed simultaneously by two pathologists assigning World Health Organization (WHO) and Gleason grades. Three-tiered Gleason grouping distributed patients into three groups (those with a score < 7, those with a score of 7, and those with a score of 8--10), whereas two-tiered Gleason categorization distributed patients into two groups (those with a Gleason score of 7A, major 3 + minor 4 patients were added to the group of patients with a Gleason score < 7 and patients with a Gleason score of 7B, major 4 + minor 3 were added to the group of patients with a Gleason score of 8--10). Univariate and multivariate analyses were performed. A P value < 0.05 was considered to be statistically significant.

RESULTS

Three-tiered Gleason grouping resulted in a relatively even distribution of the patients (44 patients had a Gleason score < 7, 58 patients had a Gleason score of 7, and 76 patients had a Gleason score of 8--10) whereas 130 patients were determined to have Grade 2 tumors based on WHO criteria. Separating those patients with a Gleason score of 7 (score 3+4 vs. score 4+3) led to the two-tiered Gleason grouping (88 patients in the favorable group and 90 patients in the unfavorable group). The two-tiered Gleason grouping displayed differences with regard to failure-free survival with the lowest P values for all patients and separately for T1/2 versus T3/4 tumors. Together with T category and pretreatment prostate specific antigen, WHO grading, three-tiered Gleason grouping, and two-tiered Gleason grouping resulted in independent parameters in the Cox regression model. The proportional variance estimate confirmed the superior discrimination for survival of two-tiered Gleason grouping.

CONCLUSIONS

The equal allocation of patients to subgroups based on the Gleason system helps the clinician to overcome the dilemma of overrepresentation of Grade 2 patients as occurs with WHO grading. The Gleason grading system and, most likely, the two-tiered Gleason grouping appear to result in better prognostic separation of patients referred to radiotherapy for relatively advanced primary tumors. Therefore the authors recommend the routine use of Gleason grading for these patients.