Diagnostic Value of Micro-Ultrasound in Identifying Local Recurrence After Radical Prostatectomy

Purpose: The limited resolution of standard transrectal ultrasound (TRUS) has made it difficult to perform biopsies of the prostate bed in cases of suspected local recurrence following radical prostatectomy. The aim of this study was to benchmark the performance of using high resolution micro-ultrasound (microUS) in place of standard TRUS for performing post-prostatectomy biopsies. Materials and methods: We conducted a retrospective review of pathology reports from January 2013 to October 2024, identifying patients who underwent biopsies of the prostate bed for suspected local recurrence after radical prostate. Sensitivity and specificity were compared for biopsies performed using standard TRUS. A biopsy was deemed diagnostic if it revealed prostate tissue (cancerous or benign) or non-prostatic tissue when a previously suspicious lesion was no longer detectable on subsequent imaging. The ground truth for local recurrence was defined by biochemical recurrence (prostate-specific antigen [PSA] ≥ 0.2 ng/mL in two consecutive measurements) accompanied by reproducible findings in the prostate bed on MRI and/or PET. Results: Of the 24 patients included, 10 (42%) underwent microUS-guided biopsy and 14 (58%) underwent TRUS-guided biopsy. The median PSA levels at biopsy for the microUS and TRUS cohorts were 0.39 ng/mL (range 0.39-6.40) and 0.45 ng/mL (range 0.20-30.82), respectively. The median lesion sizes on MRI were 0.9 cm (IQR 0.7-1.8) for microUS and 2.5 cm (IQR 1.2-6) for TRUS. MicroUS demonstrated a sensitivity of 89% (95% CI: 52-100), compared with 43% (95% CI: 18-71) for TRUS. Specificity could not be reliably assessed, as only one recurrence-negative patient was available in the microUS group and none in the TRUS group. Conclusion: MicroUS-guided transrectal biopsies appear to offer superior diagnostic performance in detecting local recurrences following radical prostatectomy compared to standard TRUS-guided biopsy. Further study is needed to confirm our findings and to evaluate the performance of microUS-guided biopsies independently of pre-biopsy imaging results.