LAUSR

PURPOSE Preoperative estimation of new-baseline glomerular-filtration-rate (NB-GFR) after partial nephrectomy (PN) or radical nephrectomy (RN) for renal cell carcinoma (RCC) has important clinical implications. However, current predictive models are either complex or lack external validity. We aimed to develop and validate a simple equation to estimate postoperative NB-GFR. MATERIALS AND METHODS For development and internal-validation of the equation, a cohort of 7860 RCC-patients undergoing PN/RN (2005-2015) at the Veteran's-Affair-National- Health-System (RCC-VA) was analyzed. Based-on preliminary-analysis of 94327 first-year postoperative GFR-measurements, NB-GFR was defined as the final glomerular-filtration-rate (GFR) within 3-12 months after surgery. Multivariable linear regression analyses were applied to develop the equation using two-thirds of the RCC-VA cohort. The simplest model with highest coefficient of determination (R2) was selected and tested. This model was then internally-validated in the remaining third of RCC-VA cohort. Correlation/bias/accuracy/precision of equation were examined. For external-validation, a similar cohort of 3012 RCC-patients from an outside tertiary-care-center (RCC-CC) was independently analyzed. RESULTS NB-GFR (ml/min/1.73m2) can be estimated with the following simplified equation: NB-GFR= 35 + preoperative GFR (x0.65) - 18 (if RN) - age (x0.25) + 3 (if tumor-size >7cm) - 2 (if diabetes). Correlation/bias/accuracy/precision were 0.82/0.00/83/-7.5-8.4 and 0.82/-0.52/82/-8.6-8.0 in the internal/external validation-cohorts, respectively. Additionally, the area-under-the-curve (95% Confidence-Interval) to discriminate postoperative NB-GFR ≥45ml/min/1.73m2 from receiver-operating-characteristic analyses were 0.90 (0.88, 0.91) and 0.90 (0.89, 0.91) in the internal/external validation-cohorts, respectively. CONCLUSIONS Our study provides a validated equation to accurately predict postoperative NB-GFR in patients being considered for RN or PN that can be easily implemented in daily clinical practice.