BACKGROUND: Strategies of active surveillance (AS) of low-risk screen-detected prostate cancer have emerged, because the balance between survival outcomes and quality of life issues when radically treating these malignancies is disputable. Delay before radical treatment caused by active surveillance may be associated with an impaired chance of curability. METHODS: Men diagnosed with low-risk (T1c/T2; prostate-specific antigen [PSA] = <10.0; PSA density, <0.2 ng/mL; Gleason score, 3 + 3=6; 1-2 positive biopsies) prostate cancer in the Swedish section of the European Randomized Study of Screening for Prostate Cancer who received radical prostatectomy (RP) were studied. One group received immediate RP, whereas another group received delayed RP after an initial period of expectant management. These groups were compared regarding histopathological and biochemical outcomes, correcting for baseline differences. RESULTS: Mean follow-up after diagnosis was 5.7 years (standard deviation [SD], 3.2). The immediate RP group (n = 158) received RP a mean of 0.5 (SD, 0.2) years after diagnosis; the delayed RP group (n = 69) received RID after 2.6 (SD, 2.0) years (P < .001). After adjustment for small baseline dissimilarities, no differences in RP frequencies of Gleason score >6 (odds ratio [OR], 1.54; P = .221), capsular penetration (OR, 2.45; P = .091), positive margins (OR, 1.34; P = .445), RP tumor volume (difference, 0.099; P = .155), or biochemical progression rates (P = .185, P = .689) were found between groups, although all data were in favor of immediate RID. CONCLUSIONS: With limited patient numbers available for analysis, differences in intermediate outcomes between immediate RP and delayed RP were nonsignificant. The delayed RP group may be subject to a selection bias. Prospective evaluation of active surveillance protocols is essential. Cancer 2010;116:1281-90. (C) 2010 American Cancer Society.