MP48-02 POSITIVE SURGICAL MARGINS PREDICT PROGRESSION-FREE SURVIVAL AFTER NEPHRON SPARING SURGERY FOR RENAL CELL CARCINOMA: RESULTS FROM A SINGLE CENTRE COHORT OF ALMOST 500 CASES WITH A MINIMUM FOLLOW-UP OF 5 YEARS

INTRODUCTION AND OBJECTIVES:The prognostic role of psecudocapsule (PC) infiltration and positive surgical margins for local recurrence after enucleative RAPN for RCC is still unknown.In this study we report a detailed histopathological analysis of the tumorparenchymal interface after enucleative RAPN, validating the recently proposed i-Cap (invasion of pseudocapsule) scoring system, and assessing its prognostic value for local recurrence at mid-long term follow-up.METHODS: Data from patients undergoing enucleative RAPN at our centre by expert robotic surgeons were prospectively collected from January 2011 to December 2013.A dedicated uropathologist classified the degree of PC infiltration according to our previously reported scheme (PC-, PCK+, PCK++) and retrospectively re-coded it according to the i-Cap scoring system (Figure 1A).Patients with benign tumors and follow-up < 48 months were excluded from the analyses.RESULTS: One hundred twenty five patients were included.PC was absent in 3 (2.4%)cases.Histopathological data according to histotypes and i-Cap score system are shown in Figure 1B and2A, respectively.At multivariable analysis, tumor histotype was the only indipendent predictor of i-Cap score (Figure 2B).Positive surgical margins were recorded in 3 (2.4%)patients.At a median follow up of 56 months (IQR 52-65), 3 cases of local recurrence were detected, all distant from the tumor enucleation bed.CONCLUSIONS: In our series, tumor histology and pT stage were the strongest predictors of PC invasion after enucleative RAPN.However, neither PC invasion nor positive margins were associated with local recurrence within the enucleation bed, confirming the oncologic safety of this technique.Further studies are needed to validate our results assessing the prognostic role of PC invasion for different resection techniques.