Validation of the Kattan preoperative nomogram for prostate cancer recurrence using a community based cohort: Results from cancer of the prostate strategic urological research endeavor (CaPSURE)

Purpose: The Kattan preoperative nomogram combines preoperative prostate specific antigen (PSA), biopsy Gleason grade and clinical stage to estimate disease recurrence after radical prostatectomy. Several studies using patient data from academic centers have validated the nomogram. We assessed the performance of the Kattan nomogram using the Cancer of the Prostate Strategic Urological Research Endeavor database, a national, largely community based observational disease registry. Materials and Methods: From the Cancer of the Prostate Strategic Urological Research Endeavor database we identified 1,701 men with clinically localized prostate cancer undergoing radical prostatectomy with sufficient pretreatment information and PSA followup after surgery. Disease recurrence was defined as 2 consecutive PSA values 0.2 ng/ml or greater, or a second cancer treatment more than 6 months after prostatectomy. A concordance index was used to evaluate the performance of the nomogram compared to observed 5-year recurrence-free survival (Kaplan-Meier). Kattan nomogram scores were calculated for each patient and stratified into 6 groups for analysis. Results: In our cohort of 1,701 men 413 (24%) had evidence of disease recurrence. Median followup, in these patients was 2.3 years. Kattan nomogram scores were 17% to 99% (mean 79%). The overall concordance index was 0.68. Varying the definition of recurrent disease and excluding patients with imputed data did not substantially alter nomogram performance (concordance index 0.65 to 0.70). The Kattan nomogram tended to overestimate 5-year freedom from recurrence in patients with scores of 65% and higher. Conclusions: We noted the reasonable performance of the Kattan nomogram for predicting cancer outcomes after radical prostatectomy using a community based population. Although concordance is lower than in previous validation studies and the nomogram overestimates recurrence-free survival in patients at lower risk, the model is fairly robust and it provides important information when counseling patients regarding treatment options in the community setting. Further refinements in pretreatment estimation of disease-free survival and ultimately overall survival are needed.