Presentation Authors: Arveen Kalapara*, Henry Pan, Mark Frydenberg, Jeremy Grummet, Melbourne, Australia
Introduction: Multiparametric magnetic resonance imaging (mpMRI) has emerged as a key tool in the diagnostic pathway of prostate cancer. Recent evidence has confirmed the accuracy of MRI-targeted biopsy in detecting clinically significant disease, suggesting the potential to omit systematic biopsy cores in the presence of a clearly positive mpMRI. However, presence of tumor in the postero-lateral peripheral zone (PL Pz) of the prostate is an important consideration in the decision to perform a nerve sparing (NS) radical prostatectomy (RP). As such, it is vital to ensure any tumor in PL Pz is visible on mpMRI prior to omitting systematic cores. We aimed to assess the incidence of clinically significant tumor in the PL Pz missed by mpMRI, and the impact of this on positive surgical margins (PSM) at the site of nerve sparing.
Methods: From a prospective single-center database we analyzed the records of men who underwent mpMRI and prostate biopsy prior to RP between 2014 and 2018. Men with PIRADS 3-5 lesions on mpMRI were divided into 2 groups. Group A included those men with any MRI lesion in the PL Pz, and Group B included those with no specifically visible lesion in the PL Pz. Clinically significant disease was defined as Gleason Score 4+3=7 or greater on RP. Mann-Whitney and Fisher's exact test were used.
Results: 412 men underwent RP following mpMRI and prostate biopsy. 385 had PIRADS 3-5 lesions on mpMRI, including 249 (64.7%) in Group A and 136 (35.3%) in Group B. Overall, 29 (7.5%), 151 (39.2%) and 205 (53.3%) had PIRADS 3, 4 and 5 lesions, respectively. There was no significant difference between Groups A and B in mean age (66.4 vs 65.5 years, p=0.193) or PSAD (0.238 vs 0.237, p=0.760). 122 (89.7%) of 136 men in Group B had tumor in PL Pz on RP, despite MRI findings, including 49 (36.0%) with clinically significant disease. 123 (90.4%) men in Group B had NS RP. 41 (30.1%) men in Group B had PSM, including 17 (12.5%) who had PSM in the PL Pz. 15 (11.0%) of these men underwent NS RP on the side corresponding to the PSM. 50 (20.1%) men in Group A had a PSM in the PL Pz. There was no significant difference between the rate of PSM in the PL Pz in Group A (20.1%) and Group B (12.5%) (p=0.068).
Conclusions: High rates of clinically significant disease are found in the PL Pz of the prostate in men undergoing RP, not specifically visible in the corresponding location on mpMRI. Hence, MRI-targeted only biopsies may risk missing tumors which could influence the decision to perform nerve-sparing RP. However, we found no significant difference in PSM between men with and without mpMRI visible lesions in PL Pz.