Can microfocal prostate cancer be regarded as low-risk prostate cancer?

PURPOSE Prostate specific antigen (PSA) screening for prostate cancer has become widespread, the prostate biopsy technique has evolved, and the occurrence of low-risk prostate cancer has been increasing. Even low-risk patients may demonstrate disease upgrading or upstaging. We aimed to evaluate the clinical importance of a single microfocal prostate cancer at biopsy in patients subsequently treated with radical prostatectomy. METHODS A total of 337 cases of patients who underwent radical prostatectomy after prostate biopsies were retrospectively reviewed. Microfocal prostate cancer was defined as Gleason score 6 and a single positive core with ≤5% cancer involvement after the standard 12-core extended biopsy. RESULTS Of the 337 prostatectomy specimens, 22 (6.5%) were microfocal prostate cancer based on prostate biopsy. On final pathology, microfocal patients were found to have significant 45% Gleason score upgrading (P=0.02) and 27% positive surgical margins (P=0.04) despite low PSA, compared with the nonmicrofocal prostate cancer group. Gleason upgrading was significantly higher in the microfocal prostate cancer group (P=0.02), whereas Gleason downgrading was significantly higher in the nonmicrofocal prostate cancer group (P<0.01). Furthermore, biochemical recurrence rate was no different between microfocal and nonmicrofocal prostate cancer at mean 31 months (P=0.18). Overall, 13 of 22 cases (53.1%) in the microfocal prostate cancer group showed Gleason upgrading or stage upgrading. CONCLUSIONS Based on higher rates of Gleason score upgrading or stage upgrading cases in microfocal prostate cancer group, compared with nonmicrofocal prostate cancer group, active surveillance should be cautiously applied to these patients.