The prognostic importance of Gleason grade in prostatic adenocarcinoma: a long-term follow-up study of 648 patients treated with radiation therapy.

PURPOSE

It is common practice to histologically grade adenocarcinoma of the prostate using the Gleason system. Whereas the prognostic utility of this grading is well known, few studies have comprehensively evaluated it for patients undergoing definitive radiation therapy and generally accepted guidelines as to which Gleason grades should be "lumped" have not been established. This study reports the results of univariate and multivariate evaluation of the prognostic significance of Gleason grade in 648 patients followed for a median of 6.5 years after radiation therapy for T1 to T4, N0, or NX, MO prostate cancer.

METHODS AND MATERIALS

The correlation between Gleason grade and local recurrence, metastatic relapse, any disease relapse, and patient survival was evaluated using univariate and multivariate methods. Analysis was also stratified according to whether the grading was assigned on a needle biopsy or on a transurethral resection specimen.

RESULTS

The large number of Gleason grades required grouping of grades for meaningful analysis and we found that a four-tier system (grades 2 and 3, 155 patients; grades 4-6, 290 patients; grade 7, 92 patients; and grades 8-10, 111 patients) correlated best with outcome. In univariate analysis, this four-tier grouping correlated significantly with local recurrence, distant metastases, any relapse, and survival. The incidences of distant metastasis at 10 years were: grades 2 and 3, 13%; grades 4-6, 34%; grade 7, 52%; and, grades 8-10, 63%. The survival rates at 10 years were: grades 2 and 3, 64%; grades 4-6, 60%; grade 7, 46%; and grades 8-10, 24%. In multivariate analysis, Gleason grade was the single most important determinant of outcome for each endpoint. These results applied equally to needle biopsy and transurethral resection specimens.

CONCLUSION

Tumor grade is the single most significant determinant of outcome following radiotherapy for clinically localized prostate cancer. The Gleason system is a valid method for grading tumors to be irradiated. A four-tier grouping into grades 2 and 3, grades 4-6, grade 7, and grades 8-10 appears to be adequate and simple.