Contemporary grading for prostate cancer: implications for patient care

Abstract

Context: The Gleason grading system is one of the most powerful predictors of outcome in prostate cancer and a cornerstone in counseling and treating patients. Since its inception, it has undergone several modifications triggered by a change in clinical practice and a better understanding of the cancer's histologic spectrum and variants and their prognostic significance.

Objective: To provide an overview of the implementation and the impact of the Gleason system as a predictive and prognostic tool in all available treatment modalities, and to compare the original and modified Gleason systems in major pathologic and clinical outcome data sets.

Evidence acquisition: A comprehensive nonsystematic Medline search was performed using multiple Medical Subject Headings such as Gleason, modified, system, outcome, biopsy, prostatectomy, recurrence, prognosis, radiotherapy, and focal therapy, with restriction to the English language and a preference for publications within the last 10 yr. All Gleason grade-related studies in the last 3 yr were reviewed. For studies before this date, we relied on prior culling of the literature for various recent books, chapters, and original articles on this topic.

Evidence synthesis: Using the modified grading system resulted in disease upgrading with more cancers assigned a Gleason score ≥ 7 than in the past. It also resulted in a more homogeneous Gleason score 6, which has an excellent prognosis when the disease is organ confined. The vast majority of studies using both systems showed that Gleason grading of adenocarcinomas on needle biopsies and radical prostatectomies was strongly associated with pathologic stage, status of surgical margins, metastatic disease, biochemical recurrence, and cancer-specific survival, with the modified system outperforming the original one in some large series. A description of the continuous incorporation of this parameter in the clinical decision making for treating prostate cancer using all currently used treatment modalities is presented, and the findings of studies before and after the inception of the modified grading system, if available, are compared. The proposed contemporary grading prognostic categories are 3+3, 3+4, 4+3, 8, and 9-10.

Conclusions: The Gleason score is one of the most critical predictive factors of prostate cancer regardless of the therapy used. Modernization of the Gleason grading system has resulted in a more accurate grading system for radical prostatectomy (RP) but has complicated the comparison of data before and after the updating. A better prognostication with the updated Gleason grading system for patients treated with modalities other than surgery can only be postulated at this time because there are limited conflicting data on radiation and no studies on other treatment modalities. Its greatest impact is the uniformly excellent prognosis associated with Gleason score 6 in RPs.