External validation and head‐to‐head comparison of Japanese and Western prostate biopsy nomograms using Japanese data sets

Abstract

The objective of this study was to perform external validation of a previously developed prostate biopsy nomogram (the CHIBA nomogram) and to compare it with previously published nomograms developed in Japanese and overseas populations. Two different cohorts of patients were used: one from the Chiba Cancer Center (n = 392) in which transperineal 16-core biopsy was performed, and another from Chibaken Saiseikai Narashino Hospital (n = 269) in which transrectal 16-core biopsy was carried out. All patients were Japanese men with serum prostate-specific antigen levels less than 10 ng/mL. The predictive accuracy of our CHIBA nomogram and of four other published nomograms (Finne's sextant biopsy-based logistic regression model, Karakiewicz's sextant biopsy-based nomogram, Chun's 10-core biopsy-based nomogram and Kawakami's three-dimensional biopsy-based nomogram) was quantified based on area under the curve derived from receiver operating characteristic curves. Head-to-head comparison of area under the curve values demonstrated that our nomogram was significantly more accurate than all other models except Chun's (P = 0.012 vs Finne's, P = 0.000 vs Karakiewicz's, and P = 0.003 vs Kawakami's). Our nomogram appears to be more useful for the Japanese population than Western models. Moreover, external validation demonstrates that its predictive accuracy does not vary according to biopsy approach. This is the first report to demonstrate that the predictive accuracy of a nomogram is independent from the biopsy method.

Between-Method Differences in Prostate-Specific Antigen Assays Affect Prostate Cancer Risk Prediction by Nomograms

“…This approach is insensitive to systematic errors in calibration, an issue that has recently been reviewed (27 ); therefore, AUC comparisons alone are not appropriate for the validation of risk calculators. ROC curve analysis has been criticized when it is used as the only tool to differentiate between 2 cohorts (28,29 ), and results can be misinterpreted (18 ). Our results, however, confirm reviewed data (8,22 ) that show a general advantage of %fPSA-based multivariate models for PCa detection.…”

“…All of these tools use the PSA value as a decisive variable for risk stratification, in addition to such other variables as a suspicious DRE result and prostate volume. External validations of various nomograms have most often been performed by applying the nomograms to different populations (16,18 ). Table 1 shows that the different results obtained with the different PSA assays greatly affect the reliability of PCa risk prediction with nomograms.…”

“…Besides tPSA, %fPSA values also differ between assays (15 ). External nomogram validation studies have not considered (11,16 ) or have considered only partially (17,18 ) the influence of PSA and %fPSA assays.…”

External validation and comparison of two nomograms predicting the probability of Gleason sum upgrading between biopsy and radical prostatectomy pathology in two patient populations: a retrospective cohort study

“…The rate of GS upgrading in low-risk patients was significantly higher in TUSMC than in CSNH (92.3% in TUSMC versus 39.3% in CSNH, P < 0.01). Although external validation was often performed using combined datasets (16)(17)(18), using just the combined datasets might cause clinicians to miss a real tendency in each institution. Thus, this suggested that clinicians should construct a calibration plot and see the tendency for each institution, when a nomogram is applied to their patients (18).…”

“…The two nomograms were externally validated in these two cohorts. To validate each nomogram externally, the area under the curve (AUC) values derived from receiver operating characteristic curves were estimated to calculate an unbiased measure of the ability of each nomogram to discriminate among patients, as described previously (16)(17)(18). The 95% confidence interval (95% CI) of the AUC values was calculated by bootstrapping.…”