Tumor Volume and Tumor Crossing of the Axial Renal Midline as Preoperative Predictors of Reduced Estimated Glomerular Filtration Rate After Robotic Partial Nephrectomy

The ability of nephrometry scoring systems, including the radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior, and location relative to polar lines (R.E.N.A.L.), to predict loss of renal function after robotic partial nephrectomy (RPN) is still controversial. Therefore, we verified which combination of factors from nephrometry scoring systems, including tumor volume, was the most significant predictor of postoperative renal function. Patients who underwent RPN for cT1 renal tumors in our hospital were reviewed retrospectively (n=163). The preoperative clinical data (estimated glomerular filtration rate [eGFR], comorbidities, and nephrometry scoring systems including R.E.N.A.L.) and perioperative outcomes were evaluated. We also calculated the tumor volume using the equation applied to an ellipsoid by three-dimensional computed tomography. The primary outcome was reduced eGFR, which was defined as an eGFR reduction of ≥20% from baseline to 6 months after RPN. Multivariate logistic regression analyses were used to evaluate the relationships between preoperative variables and reduced eGFR. Of 163 patients, 24 (14.7%) had reduced eGFR. Multivariate analyses indicated that tumor volume (cutoff value≥14.11 cm 3 , indicating a sphere with a diameter≥approximately 3 cm) and tumor crossing of the axial renal midline were independent factors for reduced eGFR (odds ratio [OR], 4.57; P=0.003 and OR, 3.21; P=0.034, respectively). Our classification system using these two factors showed a higher area under the receiver operating characteristic curve (AUC) than previous nephrometry scoring systems (AUC=0.786 vs. 0.653–0.719), and it may provide preoperative information for counseling patients about renal function after RPN.