Proteinuria is a Predictor of Renal Functional Decline in Patients with Kidney Cancer

Prior studies have shown that 26% to 34% of patients with suspected renal cancers have a glomerular filtration rate less than 60 ml/minute/1.73 m(2) but limited information exists regarding proteinuria. We investigated the extent of proteinuria in patients with renal tumors to determine the impact on the classification and progression of chronic kidney disease.

Among 1,622 patients evaluated between 1999 and 2014, 1,016 had preoperative creatinine and proteinuria measurements available. Patients were classified according to the risk of chronic kidney disease progression into low, moderately increased, high and very high risk groups according to 2012 KDIGO guidelines. Predictors of risk group and chronic kidney disease progression were analyzed using univariable and multivariate models.

Before treatment 32% had a glomerular filtration rate less than 60 ml/minute/1.73 m(2). Preoperative proteinuria was present in 22%. Proteinuria was detected in 30% with a reduced glomerular filtration rate and 18% with a normal glomerular filtration rate. Among the 44% at increased risk for chronic kidney disease progression 24%, 12% and 8% were at moderately increased, high and very high risk, respectively. The presence of proteinuria also reclassified 25% with stage III chronic kidney disease as high or very high risk. KDIGO classification predicted renal functional decline, which occurred in 2.2%, 4.4%, 9.4% and 34.6% at 3 years in low, moderately increased, high and very high risk categories, respectively. Predictors of KDIGO group included age and tumor size (each p <0.001), and the main predictors of renal functional decline were KDIGO group, tumor size and radical nephrectomy (each p <0.0001).

Identification of chronic kidney disease using only glomerular filtration rate left 18% of patients undiagnosed. The assessment of glomerular filtration rate and proteinuria classified patients according to risk of chronic kidney disease progression, identifying 44% to be at increased risk. As proteinuria predicted renal functional decline, we advocate for routine evaluation before treatment.