Prediction model for early biochemical recurrence after radical prostatectomy based on the Cancer of the Prostate Risk Assessment score and the presence of secondary circulating prostate cells.

OBJECTIVE

To establish a prediction model for early biochemical recurrence based on the Cancer of the Prostate Risk Assessment (CAPRA) score and the presence of secondary circulating prostate cells (CPCs).

PATIENTS AND METHODS

We conducted a prospective single-centre study of men who underwent radical prostatectomy as monotherapy for prostate cancer. Clinicopathological findings were used to calculate the CAPRA score. At 90 days after surgery, blood was taken for CPC detection, mononuclear cells were obtained using differential gel centrifugation, and CPCs were identified using immunocytochemistry. A CPC was defined as a cell expressing prostate-specific antigen (PSA) but not CD45. The CPC test results were defined as positive or negative. Patients were followed up for up to 5 years and biochemical recurrence was defined as a PSA level >0.2 ng/mL. The validity of the CAPRA score was calibrated using partial validation, and Cox proportional hazard regression to build three models: a CAPRA score model, a CPC model and a CAPRA/CPC combined model.

RESULTS

A total of 321 men, with a mean age of 65.5 years, participated in the study. After 5 years of follow-up the biochemical recurrence-free survival rate was 98.55%. For the model that included CAPRA score there was a hazard ratio (HR) of 7.66, for the CPC model there was an HR of 34.52 and for the combined model there were HRs of 2.60 for CAPRA score and 22.5 for CPC. Using the combined model, 23% of men changed from the low-risk to the high-risk category, or vice versa.

CONCLUSION

The incorporation of CPC detection significantly improved the model's discriminative ability in establishing the probability of biochemical recurrence; patients in the high-risk group according to CAPRA score who are negative for CPCs have a much better prognosis. The addition of CPC detection gives clinically significant information to aid the decision on who may be eligible for adjuvant therapy.