Combination of Diffusion-weighted Magnetic Resonance Imaging and Extended Prostate Biopsy Predicts Lobes Without Significant Cancer: Application in Patient Selection for Hemiablative Focal Therapy

BackgroundSignificant cancer in contralateral sides of the prostate that was missed on prostate biopsy (PBx) is a concern in hemiablative focal therapy (FT) of prostate cancer (PCa). However, extended PBx, a common diagnostic procedure, has a limited predictive ability for lobes without significant cancer.ObjectiveTo identify prostate lobes without significant cancer using extended PBx combined with diffusion-weighted imaging (DWI), which has the potential to provide pathophysiologic information on pretreatment assessment.Design, setting, and participantsWe conducted a prebiopsy DWI study between 2007 and 2012 that included 270 prostate lobes in 135 patients who underwent radical prostatectomy (RP) for clinically localized PCa.InterventionParticipants underwent DWI and 14-core PBx; those with PBx-proven PCa and who were treated with RP were analyzed.Outcome measurements and statistical analysisImaging and pathology were assessed in each side. Based on RP pathology, lobes were classified into lobes with no cancer (LNC), lobes with indolent cancer (LIC), and lobes with significant cancer (LSC). Predictive performance of DWI, PBx, and their combination in identifying lobes without significant cancer was examined.Results and limitationsLNC, LIC, and LSC were identified in 23 (8.5%), 64 (23.7%), and 183 sides (67.8%), respectively. The negative predictive values (NPV) of DWI, PBx, and their combination were 22.1%, 27.8%, and 43.5%, respectively, for lobes with any cancer (ie, either LIC or LSC), and 68.4%, 72.2%, and 95.7%, respectively, for LSC. The NPV of PBx for LSC was improved by the addition of DWI findings (p = 0.001), with no adverse influence on the positive predictive value. Limitations included a possible selection bias under which the decision to perform PBx might be affected by DWI findings.ConclusionsThe combination of DWI and extended PBx efficiently predicts lobes without significant cancer. This procedure is applicable to patient selection for hemiablative FT.