Targeted Prostate Biopsy: Umbra, Penumbra, and Value of Perilesional Sampling

Magnetic resonance imaging (MRI)-targeted prostate biopsy has an increased cancer detection rate when systematic cores are performed in addition to targeted cores. However, in using this strategy, almost 90% of biopsy cores fail to detect significant cancer. Comparatively, 90% of significant prostate cancer falls within 1 cm of the MRI region of interest. An alternative strategy for MRI-guided biopsy may be “targeted regional biopsy” where targeted cores are combined with perilesional biopsy. Systematic prostate biopsies add to the cancer detection rate of targeted biopsies, but the explanation for that increased sensitivity is not yet clear. To determine and quantify the utility of perilesional biopsies in the detection of clinically significant prostate cancer (csPCa). Participants were 2048 men with magnetic resonance imaging (MRI) lesions (grades 3–5) who underwent targeted and systematic prostate biopsy via MRI/ultrasound fusion at University of California Los Angeles and Cornell between 2011 and 2019. The study is a retrospective examination of prospectively acquired data. All biopsy cores (30191), locations of which had been stored digitally in the image-fusion device, were analyzed for tissue pathology and relationship with MRI lesions. A validated Matlab script was used to determine the distance between MRI lesions and cores containing csPCa (3552 cores from 927 men). Significance of distance measurements was determined by multilevel, multivariable logistic regression to account for within patient-biopsy correlation and control for patient characteristics. Overall, 90% (95% confidence interval [CI] = 89–91) of csPCa cores (3206/3552) were located within a radius of 10 mm from the nearest lesion: 65% (95% CI = 63–67) within the region of interest (ROI) and 26% (95% CI = 24–27) outside the ROI but within the 10-mm “penumbra.” The width of the penumbra or concentric band, which enclosed 90% of csPCa, was primarily related to MRI grade of lesion: grade 5, 5 mm; grade 4, 12 mm; grade 3, 16 mm. In 18% (95% CI = 15–20) of patients (166/927), csPCa was diagnosed only by sampling outside the MRI lesion, the yield decreasing with increasing distance. Limitations of MRI interpretation and fusion biopsy performance could affect the utility of these data in individual patients. Perilesional biopsies, that is, samples taken from a band of 10-mm radius outside MRI lesions (the penumbra), contain most cores of csPCa that are not present within the lesion. These d