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.
Keywords: Cystatin C; Glomerular filtration rate; Predictor factor; Renal cell carcinoma.