Comparison of incidentally detected prostate cancer with screen-detected prostate cancer treated by prostatectomy

BACKGROUND: The prostate may often harbor a prostate cancer (PC) which will not cause morbidity if left untreated. Screening for PC leads to increased detection of these insignificant cancers. Objective of this study is to compare PC detected by PSA screening at subsequent screening rounds and treated by radical prostatectomy (RP) with PC incidentally found in cystoprostatectomy specimens. METHODS: Radical prostatectomy specimens of 617 screen-detected PC were compared with 123 PC identified in cystoprostatectomy specimens. Surgical specimens were systematically examined and stage, grade, tumor volume were recorded. Next, we classified PC as clinically significant or insignificant (i.e., tumor volume <0.5 cm(3), absence of Gleason pattern 4/5, organ confined). Pathological features of incidentally detected PC were compared with PC detected in subsequent screening rounds and with screen-detected T1c PC. RESULTS: Screen-detected PC overall were more often multifocal, larger in volume, more advanced in tumor stage and of higher grade, while the frequency of insignificant PC was lower as compared to those in cystoprostatectomy specimens. This effect became more pronounced during subsequent screening rounds. Screen-detected T1c PC were also more often multifocal (73% vs. 37%) in average fivefold larger (0.85 cm(3) vs. 0.16 cm(3)), less often organ confined (81% vs. 94%), and less frequently clinically insignificant (33% vs. 81%). CONCLUSIONS: Screen-detected (T1c) PC treated with RP shows more aggressive features than incidentally found PC. This PSA screening-related selection seems to be mainly driven by tumor volume and-in later screening rounds-by the preferential treatment by prostatectomy of more aggressive PC.