Toward Focal Prostate Brachytherapy-Transperineal TRUS-mpMRI Fusion Prostate Biopsy using Brachytherapy Treatment Planning Systems Only

Focal prostate brachytherapy (FPB) is an emerging treatment modality for selected PCa pts. The requirements for high-quality FBP are mpMRI and TRUS-MRI guided biopsy. They result in a map of cancer distribution within different parts of the gland. There are at least several commercially available software systems to guide TRUS-MRI fusion biopsy. Unfortunately their cost exceeds the financial abilities of many brachytherapy departments. The goal of this study was to check the feasibility of TRUS-MRI fusion prostate biopsy using ONLY brachytherapy TPS. From 12.2016 to 01.2018 we performed TRUS-MRI fusion biopsies of prostate in 49 pts. The main indications for this procedure were: repeat biopsy after previously negative biopsy (35pts), suspicion of local recurrence of PCa after EBRT (8pts), other (4pts). The median age was 71 (51-84) yo. The median PSA level was 8,8 (2,13- 170) ng/ml. We defined 74 suspected lesions on MRI images. Seventeen lesions were scored PIRADS3, 27 = PIRADS4, 19 = PIRADS5, and 11 = were not scored with PIRADS (pts with suspicion of radio-recurrent tumors). MRI images were analyzed with a radiotherapy treatment planning system. In this system we also delineated prostate, suspected lesions and 5 mm margins for every lesion. Prepared images were subsequently sent to a radiotherapy treatment planning system. This system was used to perform TRUS-MRI fusion transperineal biopsy with following steps: 1. acquisition of 3D TRUS images of prostate; 2. fusion of MRI and TRUS images; 3. preplanning of the desired position of biopsy cores; 4. guidance of targeted biopsy, biopsy of 5mm margin, systematic biopsy of left and right lobe. Each biopsy core was named with template position and sent separately to Pathology Department. All data from pathology report were entered into a radiotherapy treatment planning system, resulting in 3D map of cancer distribution within the gland. We obtained verification of PCa in 67% pts. The median volume of lesion was 0.57 (0,1-9.3) cc, of lesion with 5mm margin 3.0 (2-22) cc. The median number of biopsy cores was 21 (17-27). From 74 lesions 45% were positive for PCa, with PIRADS3, 4, 5 and no PIRADS lesions being positive in 15.3%, 41.2%, 70.3% and 64% of cases, respectively. Among pts with PCa verification 33% were positive only within lesion, 61% within lesion and 5mm margin, 69.2% within lesion, margin and occupied lobe. If biological significance of PCa was added to this analysis the above-mentioned values changed to 37%, 70.4% and 79.5%, respectively. Only in 10 pts biologically significant cancer outside occupied lobe was found. Three patients experienced major toxicity (2 AUR, 1 acute prostatitis). Transperineal TRUS-MRI fusion prostate biopsy is feasible with the use of brachytherapy TPS, available at the majority of cancer centres. There is no need for extra expenses related to commercially available systems. We hope this study will help brachytherapy community to move towards focal treatment in selected pts with PCa.