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

Abstract

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.

Keywords: Gleason score; Prostate cancer; index tumor; magnetic resonance imaging; radical prostatectomy; targeted-prostate biopsy.