Gleason scores of prostate biopsy and radical prostatectomy specimens over the past 10 years

BACKGROUND: With the advent of the prostate specific antigen (PSA) assay, an increased detection rate of prostate carcinoma has ensued. This has been associated with a downward stage migration. In contrast, grade has shifted heavily toward moderate differentiation. The authors sought to test the hypothesis that such changes in grade in part may be because of trends among pathologists to upgrade similar specimens over time. METHODS: Two expert genitourinary pathologists regraded 23 prostate biopsies and 15 radical prostatectomy specimens during a 3-year period (1989-1991). Each pathologist then regraded 32 prostate biopsies and 15 radical prostatectomies from 1998 to 2000. For both time periods, each pathologist regraded only specimens that they personally had graded initially. All specimens were scored using the Gleason system, the predominant system used in describing prostate carcinoma grade. In evaluating original and regraded scores, the authors classified score changes between less than or equal to 6 and greater than or equal to 7 or between 7 and greater than or equal to 8 as significant because such changes have a high probability of altering clinical management. The results were analyzed using the two-tailed Fisher exact test. RESULTS: Of 23 prostate biopsies from 1989 to 1991, 10 of 23 (44%) had a clinically significant Gleason score change when regraded, whereas 2 of 15 (13%) radical prostatectomy specimens from the same period had a clinically significant Gleason score change. A significant change in the distribution of biopsy Gleason scores on regrading was observed (P < 0.04). In comparison, when the prostate biopsies from 1998-2000 were regraded, 10 of 32 (31%) had a clinically significant grade change. Radical prostatectomy specimens from the same period revealed 3 of 15 (20%) with a clinically significant grade change. After regrading the biopsies from 1989-1991, 8 of 23 (35%) of were upgraded, whereas 2 of 23 (9%) were downgraded. In comparison, of the biopsies with significant changes from 1998 to 2000, 3 of 32 (9%) were upgraded, whereas 7 of 32 (22%) were downgraded. Of the radical prostatectomy specimens with significant change, only 2 of 15 from each period were upgraded. Significant upgrading (P < 0.005) occurred only in the biopsy specimens from 1989 to 1991. CONCLUSIONS: The authors' data suggest that rates of upgrading and downgrading of biopsy specimens differ between the 1989-1991 cases and the 1998-2000 cases, with the 1989-1991 samples exhibiting a significant change toward higher grades. Although not excluding the possibility of a change in the biology of prostate carcinoma over time, these findings suggest that the apparent trend toward higher biopsy grades in part may be because of how pathologists interpret these specimens today as compared with 10 years ago. Therefore, outcome studies including a biopsy Gleason score from older specimens as a risk variable have a significant chance of being vulnerable to this phenomenon. Based on the authors' data, all such specimens should undergo rereview.