External validation of SPARE nephrometery score in predicting overall complications, trifecta and pentafecta outcomes following robot-assisted partial nephrectomy.

Background: There is an ongoing need and search for a simple yet accurate nephrometry scoring system for predicting the postoperative outcomes after partial nephrectomy (PN). Simplified PADUA Renal (SPARE) Nephrometry Scoring System, a simplified version of Preoperative Aspects and Dimensions Used for an Anatomical Classification (PADUA) has been proposed as a predictor of postoperative complications following PN recently. However, this score has never been externally validated and assessed as a predictor of trifecta and pentafecta outcomes of PN. In the current study, we applied the SPARE scoring system to our robot-assisted PN cohort (RAPN).

Methods: Prospectively maintained data of patients, who underwent RAPN from November 2014 to December 2018, was abstracted. Imaging was analyzed to calculate SPARE and RENAL nephrometry scores (RNS) by two urologists, independently. SPARE was compared with complications, trifecta outcomes, pentafecta outcomes, and RENAL nephrometry scoring (RNS).

Results: Data of 201 RAPN patients were analyzed. The mean SPARE score was 3 (range 0-11). One hundred thirteen patients were classified as low risk, 64 as intermediate risk, and 24 as high risks. On multivariate analysis SPARE score alone predicted complications (OR=1.37, P=0.014) and trifecta outcomes (OR=0.75, P=0.000) while age (OR=0.96, P=0.042), preoperative eGFR (OR=0.97, P=0.001) and SPARE scores (OR=0.81, P=0.016) were predictors for pentafecta outcomes. Receiver operated curve (ROC) analysis between SPARE and RNS in predicting the complications; trifecta and pentafecta outcomes had a comparable area under the curve.

Conclusions: Our study validates the SPARE nephrometry scoring system in predicting postoperative complications, trifecta, and pentafecta outcomes in a RAPN cohort. The predictive accuracy of SPARE is similar to RNS.