Improved prediction of decreased creatinine clearance by serum cystatin C: use in cancer patients before and during chemotherapy.

BACKGROUND: Serum cystatin C, a cysteine protease inhibitor, has been suggested as a new marker of glomerular filtration rate (GFR). This study explored the possibility of replacing the creatinine clearance (CrCl) estimation of GFR with cystatin C in early detection of renal impairment in cancer patients on chemotherapy.
METHODS: Serum creatinine and cystatin C concentrations as well as 24-h CrCl were determined simultaneously in 72 cancer patients. Among them, 60 were treated with combined chemotherapy with cisplatin (CDDP). Creatinine was determined enzymatically with a spectrophotometric method. Serum cystatin C was determined by a particle-enhanced turbidimetric immunoassay.
RESULTS: Cystatin C and creatinine correlated significantly (P = 0.001) with CrCl. The correlation was significantly better for cystatin C than creatinine (r = 0.84 vs 0.74; P = 0.01). Stepwise regression analysis identified no differences for the correlations between cystatin C and CrCl in patients with or without metastases (r = 0.82 and 0.84, respectively) as well as before treatment and before the fourth cycle of chemotherapy (r = 0.70 and 0.75, respectively). A cystatin C cutoff concentration of 1.33 mg/L had 87% sensitivity and 100% specificity for detecting CrCl <78 mL/min. ROC analysis indicated that cystatin C was superior to serum creatinine for predicting CrCl <78 mL/min (P <0.04).
CONCLUSIONS: Serum cystatin C is superior to serum creatinine for detection of decreased CrCl and potentially for the estimation of GFR in cancer patients independent of the presence of metastases or chemotherapy.