Do prostate cancer nomograms give accurate information when applied to European patients?

Abstract

Objective. The aim of this study was to validate and compare the performance of preoperative risk assessment tools in a population of men treated with radical prostatectomy at a single European institution. Material and methods. Patients were identified from databases of radical prostatectomy between 1996 and 2011 from a single UK centre. Information was obtained on demographics, prostate-specific antigen, staging, biopsy and specimen histopathology, and follow-up. Data were inputted into the Memorial Sloan–Kettering Cancer Center (MSKCC), Partin 1997 and Makarov/Partin 2007 nomograms, and the University of California San Francisco–Cancer of the Prostate Risk Assessment tool (UCSF-CAPRA). The risks of extracapsular extension (ECE), seminal vesicle invasion (SVI) and lymph-node involvement (LNI) were calculated and compared with known outcomes. Nomogram performance was measured using Hosmer–Lemeshow (HL) goodness-of-fit tests, calculating concordance indices (c-indices) and calibration curves. Results. Data were obtained for 541 patients. Prediction of ECE was relatively poor using all nomograms, with the Makarov/Partin 2007 the most accurate at prediction over the range of risk stratification (HL 9.9, c-index 0.62). Predictions of SVI and LNI were better than for ECE, with the MSKCC nomogram performing best for SVI (HL 10.9, c-index 0.73) and all nomograms performing well for LNI prediction (c-indices 0.8 to 0.815). CAPRA predicted best for SVI (OR 1.49, 95% confidence interval 1.27–1.74). Conclusions. To the authors’ knowledge, this is the first head-to-head comparison of the accuracy of these commonly used risk calculators in a North European population. Caution should be used when counselling patients using nomograms. Although nomograms may be used as a guide, patients should be warned that they often have not been validated on different European populations and may give misleading information regarding a patient’s specific risks.

Key Words:

• cancer
• nomogram
• prostate.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.