How localized is pathologically localized prostate cancer? The use of secondary circulating prostate cells as a marker of minimal residual disease and their association with patient outcome.

Objective To determine the prognostic value of secondary circulating prostate cells (CPCs) in men with pT2 prostate cancer treated with radical prostatectomy. Material and methods Prospective observational study was performed in men with pathologically confined prostate cancer who had been treated with radical prostatectomy. CPCs were obtained by differential gel centrifugation from 8 mL venous blood and identified by standard immunocytochemistry using anti-Prostate Specific Antigen (PSA) monoclonal antibody. A positive test was defined as ≥1 PSA staining cell/blood sample. Biochemical failure was defined as a serum PSA >0.2 ng/mL. Age, PSA at diagnosis, pT2a versus pT2b/c, Gleason score and the presence/absence of CPCs were compared with patient outcomes using Kaplan-Meier curves and Cox's hazard model. Results Hundred and ninety-one men participated in the study, 107 (44.0%) had pT2b/c disease, 25 (13.1%) had a Gleason score ≥7, and 39 (20.4%) were positive for CPCs. Biochemical failure occurred in 39 (20.4%) patients which was associated with a Gleason score ≥ 7 and CPCs (+). Survival rates at 3, 5 and 10 years for men with CPC (-) and CPC (+) were 100%, 100% and 89.6%, and 74.4%, 64.1% and 18.5% respectively (HR: 18.70). The median time to failure was 5.1 years in CPC (+) men versus 8.1 years in CPC (-) patients. Conclusion Secondary CPC is a marker for minimal residual disease and it is associated with a worse prognosis. The lead time to failure over serum PSA is approximately 5 years. However they do not define whether the failure is local or systemic.