RESECTION TECHNIQUES FOR NEPHRON SPARING SURGERY VARY: INSIGHTS FROM A PROSPECTIVELY COLLECTED MULTIINSTITUTIONAL COHORT HARNESSING THESURFACE-INTERMEDIATE-BASE (SIB) MARGIN SCORE (SIB INTERNATIONAL CONSORTIUM)

Introduction/Aim: Resection methodology is rarely reported in current nephron-sparing surgery (NSS) literature. Yet, a relationship between resection technique (RT) and complication rates, preserved parenchymal volume, surgical margins and oncologic outcomes likely exists. The aim of the study was to evaluate the newly proposed Surface- Intermediate-Base (SIB) margin score as a standardized reporting system of RT in a cohort of patients undergoing NSS at 16 high-volume Centers across the U.S. and Europe. Materials and Methods: After Institutional Review Board’s approval, data were prospectively collected over a 6-month enrollment period. Results: A total of 507 patients were finally enrolled in the study. The mean number of patients included per center was 32 (range=11-90). A mix of open (150, 29.4%), laparoscopic (67, 13.2%) and robotic (290, 57%) approaches were harnessed for NSS. The median interquartile range (IQR) of pre-operative tumor size for the entire cohort was 3.10 cm (2.50-4.30). Based on the PADUA score, 195 (38.5%), 188 (37.1%) and 114 (22.5%) tumors were classified as low (PADUA 6-7), moderate (PADUA 8-9) and high (PADUA 10- 13) complexity tumors, respectively. At pathological analysis,30 (5.9%) positive surgical margins were recorded. Overall, the Trifecta outcomes (defined as absence of perioperative complications, negative surgical margins and warm ischemia time (WIT)<25 min) were achieved in 370 (73%) of patients. A snapshot of RTs performed in the entire cohort according to the SIB margin score is presented in Figure 1. The overall RT was classified as pure enucleation (SIB 0-1), hybrid enucleation (SIB 2), pure enucleoresection (SIB 3), hybrid enucleoresection (SIB 4) and resection (SIB 5) in 174 (34.3%), 92 (18.1%), 106 (20.9%), 44 (8.7%) and 91 (17.9%) patients, respectively. Conclusion: Standardized reporting of resection technique is lacking in the current NSS literature. We recently introduced a standardized scoring system, the SIB margin score, which quantitates the salient aspects of resection approaches after PN through a visual analysis of the intrarenal portion of the specimen immediately after surgery. Harnessing this systematic characterization of renal mass RTs, in an international multi-institutional cohort, we -for the first timedemonstrated that resection approaches vary and renal tumor enucleation is employed quite frequently even at institutions that do not support its ubiquitous use. These data lay the groundwork for determining whether RT is a modifiable variable for functional and oncologic outcomes in patients who undergo NSS.