Comparing Image-guided targeted Biopsies to Radical Prostatectomy Specimens for Accurate Characterization of the Index Tumor in Prostate Cancer

Aim: To evaluate the accuracy of multiparametric magnetic resonance–transrectal ultrasound fusion targeted biopsy (TBx) in the characterization of the index tumor, as confirmed by association with radical prostatectomy (RP) specimens. Patients and Methods: A total of 152 patients with TBx-confirmed prostate cancer (PCa) underwent robot-assisted RP. Stained whole-mount histological sections were used as the reference standard. All lesions with a volume >0.5 ml and/or pathological Gleason score (GS) >6 were defined as clinically significant PCa. The index lesion was defined as the largest tumor focus within the prostate gland. Results: The pathological index tumours included: 147 lesions (96.7%) with a volume >0.5 ml and five (3.3%) with a volume ≤0.5 ml, but with a pathological GS ≥7; 135 (88.8%) were located in the peripheral zone. TBx accuracy in the detection of the correct site of the index lesion by reference standard was 82.2%. Sensitivity, specificity, positive and negative predictive value were: 82.3%, 50.4%, 82.8% and 49.7%, respectively. The primary/secondary Gleason grade and GS of the 152 index tumors were properly estimated in 130 (85.5%), 115 (75.6%) and 127 (83.6%) cases, respectively. The concordance of TBx with pathological GS was 83.6%. The rate of up-grading and down-grading of TBx Gleason sum was 12.2% and 4.2%, respectively. Conclusion: TBx has a high sensitivity for characterization of index lesions, with a good concordance for topographic and Gleason grading accuracy between biopsy and surgical specimens.

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