A new tridimensional effective method to calculate Real Contact Surface Area (RCSA) between renal tumor and surrounding kidney parenchyma: An Innovative Tool with predictive power of intraoperative outcomes in nephron sparing surgery

Abstract

The Contact Surface Area (CSA) is a predictor for peri-operative parameters and represent the contact area between the tumor and the respective organ. Nowadays, a precise method for calculating CSA is yet to be found in the literature. We tested a new CSA calculation method as a predictor of intra-operative parameters in robot assisted partial nephrectomy (RAPN). The study population consisted of all consecutive patients treated with RAPN at a single high-volume European institution (between 2020 to 2023; 82 patients). We proposed a new method to measure the real value of CSA using an algorithm that leverages the geometry of kidneys and tumors obtained from 3D reconstruction. These reconstructions were obtained using the certified medical software Materialized Mimics InPrint. Peri-operative parameters of patients were recorded in an anonymous database. We explored the correlation between RCSA, CSA of Hsieh (HCSA), PADUA and R.E.N.A.L. scores with peri-operative parameters using Spearman correlation. Furthermore, we examined which of RCSA, PADUA and R.E.N.A.L. score better describes the intra-operative parameters, Warm Ischemia Time (WIT), Operating Time (OT), and Estimated Blood Loss (EBL) using Receiver Operating Characteristic (ROC) curve analysis. Multivariable linear regression analyses were performed. We observed a significant correlation between RCSA and WIT, OT and EBL. Moreover, RCSA outperformed both the PADUA and R.E.N.A.L. score as demonstrated in the ROC curve analysis. In ROC analysis was chosen a threshold for each of the parameters: for WIT 20 minutes, for OT 180 minutes and for EBL 200 mL. At multivariable regression analysis, RCSA emerged as the only independent predictor for WIT, OT and EBL (B=0.39 & p=0.03, B=0.35 & p=0.01, B=0.48 & p<0.001, respectively). Our original and effective 3D RCSA calculation method was favorably associated to intra-operative surgical outcomes. As compared to PADUA and RENAL score, our calculated RCSA represented a better predictor of intra-operative parameters.