Impact of Reduced Glomerular Filtration Rate and Proteinuria on Overall Survival of Patients with Renal Cancer.

PURPOSE: Although it is commonly staged according to glomerular filtration rate, an international work group recommended classifying chronic kidney disease by cause, glomerular filtration rate and albuminuria. Data on nonsurgical patients with chronic kidney disease indicate proteinuria to be an independent predictor of renal function decrease and mortality. We evaluated whether preoperative proteinuria impacted survival in patients undergoing nephrectomy. MATERIALS AND METHODS: An institutional registry was queried for information regarding preoperative creatinine/glomerular filtration rate and urinalysis in 900 patients, including 362 and 538 treated with partial and radical nephrectomy, respectively. Patients were grouped according to glomerular filtration rate level (G1 to G5), proteinuria level (A1 to A3) and chronic kidney disease risk classification (low to very high). Kaplan-Meier and Cox proportional hazards analyses of overall survival were performed. RESULTS: The preoperative glomerular filtration rate was less than 60 ml/minute/1.73 m(2) in 30% of patients (median 73, IQR 56-91) and 20% of patients had baseline proteinuria. According to the KDIGO (Kidney Disease Improving Global Outcomes) classification 23% of patients were at moderately increased, 11% were at high and 8% were at very high risk for chronic kidney disease progression. Kaplan-Meier analysis revealed that the preoperative glomerular filtration rate, proteinuria and chronic kidney disease risk group were associated with poor overall survival. In Cox proportional hazard models accounting for age, gender, race, tumor size, clinical stage and surgery type the glomerular filtration rate, proteinuria and chronic kidney disease risk group were highly significant predictors of overall survival (p <0.0001). CONCLUSIONS: Preoperative proteinuria is a significant predictor of overall survival in patients who undergo nephrectomy. Classification according to preoperative glomerular filtration rate and proteinuria more accurately predicts survival than using the glomerular filtration rate alone after accounting for cancer stage. This information supports routine evaluation of proteinuria in patients with kidney cancer.

Surgeon assessment of renal preservation with partial nephrectomy provides information comparable to measurement of volume preservation with 3-dimensional image analysis.

PURPOSE: The strongest predictors of renal function after partial nephrectomy are the preoperative glomerular filtration rate and the amount of preserved parenchyma. Measuring volume preservation by 3-dimensional imaging is accurate but time-consuming. Percent functional volume preservation was designed to replace surgeon assessment of volume preservation with a less labor intensive, objective assessment. We compared volume preservation with 3-dimensional imaging, percent functional volume preservation and surgeon assessment of volume preservation as predictors of renal function after partial nephrectomy. MATERIALS AND METHODS: We calculated volume preservation with 3-dimensional imaging, percent functional volume preservation and surgeon assessment of volume preservation in 41 patients with preoperative and postoperative cross-sectional imaging available. Surgeon assessment was validated internally in another 75 patients. Short-term and long-term renal function was assessed with univariate and multivariate linear regression models. RESULTS: Median parenchymal preservation was 85% (range 37% to 105%) by 3-dimensional imaging, 91% (range 51% to 114%) by percent functional preservation and 88% (range 45% to 99%) by surgeon assessment. Each method strongly correlated with nadir glomerular filtration rate (r(2) = 0.75, 0.65 and 0.78) and latest glomerular filtration rate (r(2) = 0.65, 0.66 and 0.67, respectively, each p <0.0001). Univariate analysis revealed that age, preoperative glomerular filtration rate, renal nephrometry score and each assessment were significant predictors of renal function (p <0.05). On multivariate analysis parenchymal preservation was the strongest predictor (p <0.0001). Models using volume preservation with 3-dimensional imaging, percent functional volume preservation and surgeon assessment of volume preservation were statistically similar in the ability to predict the nadir and latest glomerular filtration rates. In an additional validation cohort surgeon assessment remained strongly correlated with nadir glomerular filtration rate (r(2) = 0.74) and latest glomerular filtration rate (r(2) = 0.73, each p <0.0001). CONCLUSIONS: Surgeon assessment of volume preservation provides a reliable estimate of renal functional preservation with characteristics comparable to those of more time intensive alternatives. We propose that surgeon assessment of volume preservation should be routinely reported to facilitate analysis of partial nephrectomy outcomes.