PREDICTIVE FACTORS OF RESECTION TECHNIQUES DURING PARTIAL NEPHRECTOMY IN A COHORT OF “ENUCLEORESECTIVE” CENTERS: INSIGHTS FROM THE SURFACEINTERMEDIATE- BASE (SIB) MARGIN SCORE INTERNATIONAL CONSORTIUM

Introduction: Detailed reporting of resection strategies (RS) and resection techniques (RT) for tumor excision during partial nephrectomy (PN) is lacking in the current literature. The aim of the study was to evaluate (i) possible correlations between patients’ and/or tumors’ characteristics and RT performed and (ii) whether the type of RT does influence perioperative outcomes after PN, harnessing the newly proposed Surface- Intermediate-Base (SIB) margin score as a standardized reporting system. Materials and Methods: After Institutional Review Board’s approval, data were prospectively collected from a cohort of 507 patients undergoing NSS at 16 highvolume Centers across the U.S. and Europe over a 6-month enrollment period. RT was classified according to the SIB score. RS was classified as “enucleative”, “enucleoresective” or “resective” according to the most prevalent RT performed in each centre’s cohort. Descriptive and comparative analyses were performed in the six enucleoresective RS centres (ERC). Results: Overall, 507 patients were finally enrolled in the study. The RT was classified as pure or hybrid enucleation (E, SIB 0- 2), pure or hybrid enucleoresection (ER, SIB 3-4) and resection (R, SIB 5) in 266 (52.5%), 150 (29.6%) and 91(17.9%) patients, respectively, in the overall cohort, while in 53 (33.1%), 83 (51.9%) and 24 (15.0%) patients in the ERC. Demographic data, comorbidity scores, surgical indication and approach and PADUA score did not significantly differ between the E, ER and R groups in the ERC. Tumors >4.0 cm were 21 (40.4%), 41 (49.4%) and 4 (16.7%) in the E, ER and R groups (p=0.02), respectively. A clampless strategy was used in 19.2%, 13.2% and 8.3% of patients (p>0.05). Median warm ischemia time (WIT) was 19 (15-24), 17 (14-23) and 17 (15- 21) minutes in the E, ER and R groups (p>0.05). Surgical postoperative complications were recorded in 7.5%, 13.2% and 4.2% of patients (p=0.05). Positive surgical margin rate was 7.0%, 13.4% and 0% of patients, respectively (p>0.05). Trifecta outcome was achieved in 67.2%, 71.6% and 73.7% of patients for the E, ER and R groups (p>0.05). Discussion and Conclusions: This is the first study evaluating pre-operative predictive factors of RTs performed during PN and whether the type of RT significantly impacts on NSS outcomes using a standardized instrument of reporting. Overall, in ERC, ER represents less than 52%. ER and E are performed in a significantly higher proportion of tumors >4 cm compared to R. Relating to surgical outcomes, ER was associated with a significantly higher rate of post-operative surgical complication compared to E and R. However, Trifecta achievement was comparable among the three techniques.