Purpose: Gleason grading is the strongest predictor of prostate cancer outcome and commonly used to decide for or against the different treatment options. However, Gleason upgrading between systematic transrectal ultrasound-guided prostate biopsy (TRUS-GB) and radical prostatectomy (RPE) has frequently been observed. With respect to the high accuracy of multiparametric MRI (mpMRI) for high-grade cancers and the higher percentage of cancer involvement per biopsy core in targeted MR-guided prostate biopsy (MR-GB), we hypothesized that MR-GB reduces the risk of Gleason upgrading on RPE as compared to the gold standard. The purpose of this study was to compare the rate of Gleason upgrading on RPE for MR-GB, TRUS-GB, and the combination of both biopsy modalities.
Methods: Overall, 52 consecutive patients with RPE had received an mpMRI of the prostate and subsequently underwent targeted MR-GB prior to surgery. All patients underwent an additional TRUS-GB during the same biopsy session. Gleason grading was measured by two different methods: the conventional Gleason score (cGS = primary + secondary pattern) and the highest Gleason pattern (hGP).
Results: In relation to TRUS-GB, MR-GB alone showed lower rates of upgrading when comparing the cGS (40.4 vs. 50.0 %) and the hGP (21.2 vs. 32.7 %). The combination of MR-GB and TRUS-GB showed the lowest rates of upgrading (cGS: 28.8 %; hGP: 11.5 %), and compared to TRUS-GB, significantly reduced the risk of upgrading for both measurements of Gleason grading (cGS: OR 0.41, 95 % CL 0.18-0.91, p = 0.0289; hGP: OR 0.27, 95 % CL 0.10-0.75, p = 0.0123).
Conclusion: MpMRI and targeted MR-GB are useful tools to better characterize and stage the extent of disease, and therefore enable the urologist to better risk-stratify and counsel the patient. The combined use of targeted MR-GB and TRUS-GB presents the least risk of Gleason underestimation.
Keywords: Gleason grading; Gleason score; Image-guided prostate biopsy; MR-guided prostate biopsy; Magnetic resonance imaging; Prostate cancer.