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.