Purposes: To develop a new predictor and update nomogram based on prostate imaging reporting and data system version 2 (PI-RADS V2) in predicting intermediate- and high-risk prostate cancer (IH-Pca) and reducing the overtreatment for low-risk Pca (L-Pca).
Methods: All men that underwent trans-rectal ultrasound-guided 12+X-core prostate biopsy between January 2015 and June 2018 were collected and analyzed. The significant risks (SRs) of Pca were selected by univariate and multivariate analysis. All SRs were divided into four groups (0 to 3 points) based on the probability of PI-RADS. Each patient can obtain a total score (TS). The updated nomogram was established by R package version 3.0. The area under the curve (AUC), net reclassification index (NRI), calibration curves and decision curves were used to evaluate the diagnostic performance.
Results: There were 1,078 patients, including 640 (59%) men with normal or L-Pca (N-LPca) and 438 (41%) men with IH-Pca. The scores of TS for IH-Pca and N-LPca were 16.13±3.11 and 10.52±3.32, respectively (P <0.01). The discriminative power of TS and nomogram was comparable in predicting IH-Pca (AUCs: 0.88 vs 0.87, P =0.89), and both were greater than PSA and PI-RADS (AUCs: 0.76 vs 0.80). For NRI, NRI_{TS vs nomogram} was 1.31% (P =0.55), NRI_{TS vs PSA} was 24.13% (P <0.001) and NRI_{TS vs PI-RADS} was 13.19% (P <0.001). Compared with PSA, PI-RADS and nomogram, TS can reduce the number of unnecessary biopsies, up to 71%, 60% and 38%, respectively.
Conclusion: The new predictor is comparable to the updated nomogram in predicting IH-Pca, and both are better than PSA and PI-RADS. In addition, the new predictor slightly outperforms nomogram in reducing the unnecessary biopsies for L-Pca and being convenient to use.
Keywords: age, PSA, PSA density, prostate cancer detection, PI-RADS, nomogram