LAUSR

INTRODUCTION AND OBJECTIVE: The RENAL nephrometry score (RNS) is widely used to describe renal mass complexity and inform patient counseling for partial nephrectomy (PN). However, in cases with multiple lesions (commonly seen in hereditary cancer syndromes) it is unknown which features drive postoperative complications. Here, we employed a novel scoring equation (Multiplex Score, MS) derived from RNS and assessed outcomes of multiplex PN at our institution. METHODS: The MS was defined a priori as a weighted score (# low risk (LR) lesions) þ 2*(# intermediate risk (IR)) þ 4*(# high risk (HR)) based on published Clavien-Dindo III-V complication rates of 6.4%, 11.1%, and 21.9% for LR, IR, and HR RNS respectively. MS was dichotomized into favorable/unfavorable based on median score. Patient outcomes were maintained prospectively. Binary outcomes were evaluated with logistic regression and continuous outcomes were evaluated with linear regression. RESULTS: From 10/2017-8/2019, 62 consecutive multiplex PN (median (range) # tumors[ 4 (2-11), 65% robotic) were performed by a single surgeon. Median (range) MS was 6 (2-20). Of 13 complications, urine leak (N[5, 8%) and bleed requiring embolization (N[4, 6%) were the most common. Only 1 complication occurred in the favorable score group and MS was significantly associated with perioperative complication (OR 1.21, p[0.018) and blood loss (242.42 mL, p<0.001). Hilar clamping was omitted in 32 (52%) cases with median 18.5 min when used. Every 1 additional HR or IR tumor was associated with a 2 minute increase in clamp time (2.01, p[0.048). Median clamp time for favorable/unfavorable cases was 0 vs. 10 minutes. Change in renal function was negligible in our cohort (median DCr 0 mg/dL, IQR -0.61 e 0.1). There were no conversions from partial to radical nephrectomy and open conversion was only done in 3 (7.5%) cases, all assigned unfavorable MS. CONCLUSIONS: The novel Multiplex Score associated well with complications, blood loss, and open conversion. This tool may facilitate standardized reporting of complexity for multiplex series, with special relevance for hereditary cancer syndromes.