Combined T2 and diffusion-weighted MR imaging with template prostate biopsies in men suspected with prostate cancer but negative transrectal ultrasound-guided biopsies

Abstract

Purpose: Transperineal template prostate (TPB) biopsy has been shown to improve prostate cancer detection in men with rising PSA and previous negative TRUS biopsies. Diagnostic performance of this approach especially MR imaging and using reliable reference standard remains scantly reported.

Materials and methods: A total of 200 patients, who were previously TRUS biopsy negative, were recruited in this study. All the participants had at least 28-core TPB under general anesthetic within 8 weeks of previous negative TRUS biopsies. In 15 men undergoing laparoscopic radical prostatectomy, prostate specimens were sectioned using custom-made molds and analyzed by experienced pathologist as a feasibility study.

Results: In total, 120 of 200 patients (60 %) had positive TPB biopsy results. All of these men had at least one negative biopsy from transrectal route. T2 diffusion-weighted MR imaging showed no lesion in almost one-third of these men (61/200; 30.5 %). Out of these, 33 (33/61; 54 %) showed malignancy on TPB including high-grade tumors (>Gleason 7). Out of 15 patients underwent surgery with a total of 52 lesions (mean 3.5) on radical prostatectomy histology analyses, TPB detected 36 (70 %) lesions only. Some of these lesions were Gleason 7 and more mostly located in the posterior basal area of prostate.

Conclusions: Transperineal template biopsy technique is associated with significantly high prostate cancer detection rate in men with previous negative TRUS biopsies, however compared to radical prostatectomy histology map, a significant number of lesions can still be missed in the posterior and basal area of prostate.

Keywords: Diffusion-weighted imaging (DWI); Multiparametric MRI (mpMRI); Prostate cancer (PCa); T2-weighted image (T2WI); Transperineal template biopsy (TPB); Transrectal ultrasound (TRUS).

Fig. 1

Flow chart of study. One of the prostate lesions shows in T2-weighted MR images (a, red arrow); template prostate biopsy (b, red mass area); prostatectomy specimen slice (c, red arrow); and histology photo (d, red arrow). Asterisk: Pre-TPB is within 8 weeks of previous negative TRUS biopsies

Fig. 2

Steps of patient-specific molds fabrication and histopathological sectioning—1 segmentation of MRI data in biomedical software MIMICS, 2 mold fabrication in CAD software SolidWorks, 3 3D printout from rapid prototyping machine MakerBot, 4 post-radical prostatectomy specimen before dyeing and mold placement, 5 slicing of prostate specimen with a single blade, 6 sliced sections shown in the mold and 7 specimen slices arranged from apex to base

Fig. 3

Segmentation of the prostate (green area) in three different views of MR imaging, from left to right axial, coronal and sagittal

Fig. 4

Patient outcome and lesion detection in different methods

Fig. 5

Distribution of cancer foci in 36 patients with negative MRI and positive TPB