MP15-05: Topographic Description of the Site of Positive mpMRI and Impact on the Risk of Positive Surgical Margins at Robot-Assisted Nerve Sparing Radical Prostatectomy. Implications for Accurate Surgical Approaches

Francesco Barletta*, Giorgio Gandaglia, Giuseppe Rosiello, Simone Scuderi, Armando Stabile, Elio Mazzone, Milano, Italy, Nicola Fossati, Andrea Gallina, Lugano, Switzerland, Emanuele Zaffuto, Umberto Capitanio, Alessandro Larcher, Milan, Italy, Andrea Salonia, Milano, Italy, Federico Dehò, Varese, Italy, Pierre I. Karakiewicz, Montreal, Canada, Shahrokh F. Shariat, Vienna, Austria, Vincenzo Mirone, Napoli, Italy, Francesco Montorsi, Alberto Briganti, Milano, Italy

Introduction: Multiparametric MRI (mpMRI) might reduce the risk of positive surgical margins (PSM) in men with non-palpable prostate cancer (PCa). However, its role might vary according to the location of the index lesion. We hypothesized that the site of mpMRI positivity might impact on the risk of PSM in men undergoing nerve-sparing robot-assisted radical prostatectomy (nsRARP).

Methods: Overall, 307 PCa patients diagnosed with mpMRI-targeted biopsy and treated with nsRARP at a referral center between 2018 and 2021 were identified. Among those, 283 had detailed information on the site of the index lesion and on the presence of extracapsular extension at mpMRI (rECE) and represented the study cohort. All patients had details on the site and location of ECE and PSM (i.e., malignant cells in contact with the inked surface of the prostate) at final pathology. The proportion of PSM at the site of the index lesion (namely, concordant) and not concordant with the index lesion location was assessed using contingency tables. The chi-square compared proportions between groups. Logistic regression analyses evaluated the impact of the index lesion location on the risk of having a concordant PSM.

Results: Median age and PSA were 66 years and 6.4 ng/ml. Overall, 5 (2%), 201 (71%) and 77 (27%) patients had grade group 1, 2-3, and 4-5. The median index lesion volume was 0.5 cc. Overall, 54 (19%), 147 (52%) and 82 (29%) patients had an index lesion at the base, lateral side, and apex. Among those, 8, 17 and 6 patients had rECE at the base, lateral side and apex. Overall, 40 (14%) patients had PSM and the rate was 20%, 47% and 32% at the base, lateral side and apex. The site of PSM was concordant with the index lesion in 15/40 (37%) patients. When stratifying patients with PSM according to the index lesion location at mpMRI, the proportion of men with a concordant PSM was higher among those with a lesion at the base (75%) vs. lateral (31%) vs. base (23%). At multivariable analyses, an index lesion at the base was associated with a 4-fold higher risk of a concordant PSM in men with positive margins (p=0.01).

Conclusions: Men with lesions located at the base have a higher risk of a PSM located at the same site. Conversely, individuals with a lesion at the lateral margin or apex have a higher risk of harboring a PSM elsewhere. These findings should help surgeons in guiding the optimal extent of the dissection during nsRARP.

Source of Funding: none