Cystatin C as a predictor factor in patients with renal cell carcinoma treated by everolimus

Background We evaluated the influence of serum cystatin C (CysC) with respect to other glomerular filtration rate (GFR) markers on the treatment effect of everolimus in a phase II study in patients with metastatic renal cell carcinoma (mRCC). Materials and methods Outcomes were from the study’s primary analysis. GFR was calculated according to CKD-EPI-sCr equation, CKD-EPI-CysC equation and CKD-EPI-sCr-CysC equation, Modification of Diet in Renal Disease (MDRD) equation and Cockcroft–Gault (CG) equation, serum levels of creatinine (sCr) and CysC before the treatment. Results We observed in 56 patients analysed patients high correlation ( R Spearman from ±0.69 to ±1.00; P < 0.0001) between CysC level and GFR markers: sCr, CKD-EPI-sCr, CKD-EPI-CysC, CKD-EPI-sCr-CysC, MDRD, GFR (CG) before everolimus therapy. We observed that the adverse independent predictors for everolimus therapy were increased CysC level [HR: 2.85 (95 % CI 1.34–6.05), P = 0.0065], histologic grade G1/2 [HR: 3.38 (95 % CI 1.59–7.20), P = 0.0016] and increased LDH level [HR: 5.59 (95 % CI 2.52–12.40), P < 0.0001]. Worse OS was seen in multivariate analysis in patients with increased cystatin C level before treatment [HR: 2.60 (1.03–2.60), P = 0.0428], increased corrected calcium level [HR: 2.78 (95 % CI 1.03–7.54), P = 0.0441] and increased LDH level before treatment [HR: 2.34 (95 % CI 1.11–4.97), P = 0.0262]. Conclusion Increased serum CysC level in contrast to other studied GFR markers had predictive significance in patients with mRCC.