Cystatin C as a Parameter of Glomerular Filtration Rate in Patients with Ovarian Cancer

Aims: To evaluate the potential role of serum cystatin C as a marker of renal function in patients with ovarian cancer. Methods: Treatment of consecutive ovarian cancer patients who were eligible for chemotherapy with paclitaxel (135 mg/ m 2 /24 h) and cisplatin (75 mg/m 2 ) every 3 weeks in 6 cycles. Glomerular filtration rate (GFR) markers, i.e. serum levels of creatinine and cystatin C, estimated by the Cockcroft-Gault and Modification of Diet in Renal Disease formulas, were recorded before each cycle and 3 weeks after the 6th course. Results: The median age of 34 patients was 54 years. In the initial stage of treatment, we did not observe any correlation between cystatin C and other GFR markers. We noted a significant association between cystatin C and tumor extent on spiral CT scans (diameter: 1 1 cm) performed at baseline (p = 0.004), and after the 1st (p = 0.03) and 2nd cycle (p = 0.026). We observed a correlation between cystatin C and CA-125 level before chemotherapy (R = 0.4; p = 0.02) and after the 1st cycle (R = 0.43; p = 0.04). Conclusion: The results of our study suggest that cystatin C is not a reliable marker of the GFR in ovarian cancer patients, probably due to its nature as a cysteine protease inhibitor. Copyright © 2010 S. Karger AG, Basel Received: January 19, 2010 Accepted: July 11, 2010 Published online: August 17, 2010 Lubomir Bodnar Military Institute of Medicine Szaserów 128 PL–04-141 Warsaw (Poland) E-Mail lubo @ esculap.pl © 2010 S. Karger AG, Basel 1420–4096/10/0335–0360$26.00/0 Accessible online at: www.karger.com/kbr D ow nl oa de d by : 54 .7 0. 40 .1 1 10 /6 /2 01 7 4: 57 :3 5 A M Cystatin C and GFR in Patients with Ovarian Cancer Kidney Blood Press Res 2010;33:360–367 361 Recent investigations suggest that cystatin C may be a better filtration marker than creatinine, especially at higher levels of GFR [4] . Cystatin C, a cysteine proteinase inhibitor, is a 120-amino-acid basic protein (molecular weight: 13 kDa) produced by nearly all human cells and released into the bloodstream, filtered by the kidney glomerulus and metabolized in the proximal tubule. This protein belongs to the cystatin superfamily of cysteine protease inhibitors. The production rate of cystatin C is stable and does not change in inflammatory conditions. Cystatin C is influenced by glucocorticoids and thyroid dysfunction [5, 6] . In different clinical trials, cystatin C has been supposed to represent an alternative endogenous GFR marker due to the fact that it is not secreted but reabsorbed by tubule epithelial cells, then catabolized and eliminated mainly by glomerular filtration [7, 8] . In malignancy, an imbalance between cysteine proteases and their inhibitors, associated with a metastatic tumor cell phenotype, is thought to facilitate tumor cell invasion and metastasis [9] . Numerous studies have provided evidence of substantial increases in mRNA, protein and the activity of tumor cysteine proteases, accompanied only by a moderate increase in, or unchanged concentrations of, intracellular inhibitors [10] . Enhanced extracellular secretion of cysteine proteases is another feature associated with tumor cell phenotype. A few studies reported that cystatin C levels are elevated in malignant tissues and in body fluids of patients with neoplastic diseases including breast cancer and prostate cancer. This phenomenon is associated with more aggressive forms of these tumors [11–13] . To evaluate its validity in ovarian cancer patients with normal kidney function (GFR 1 60 ml/min/1.73 m 2 estimated by MDRD formula) treated with cisplatin-based chemotherapy, serum concentrations of cystatin C and serum creatinine were analyzed and compared with respect to GFR estimation during first-line chemotherapy. Patients and Methods Patients The clinical trial design has been previously described [14] . In brief, a prospective, randomized, placebo-controlled and doubleblind phase II trial was conducted at the Department of Oncology, Military Institute of Medicine, Warsaw, Poland. First, 34 consecutive patients with ovarian cancer after primary surgery, without history of renal diseases, without deviations from normal kidney morphology in imaging studies, with normal kidney function (GFR 1 60 ml/min/1.73 m 2 estimated by MDRD formula) and qualifying for first-line chemotherapy were prospectively included. The study protocol was approved by the local ethics committee, and written informed consent was obtained from all participants. The patients were assigned to receive 6 courses of first-line chemotherapy consisting of 135 mg intravenous paclitaxel per square meter of body surface area over a 24-hour period on day 1 followed by 75 mg intravenous cisplatin per square meter on day 2. Standard premedication (dexamethasone 20 mg, clemastine 1 mg and ranitidine 150 mg) was given intravenously to prevent hypersensitivity reactions to paclitaxel. The treatment was administered every 3 weeks in 6 cycles. Hydration (3,000 ml of 0.9% NaCl) and antiemetic agents (ondansetron 8 mg) were administered intravenously before cisplatin. The study medication, magnesium sulfate and magnesium subcarbonate, was administered as previously described [14] . Laboratory Methods Serum levels of creatinine, and the ClCG and MDRD formulas were recorded before each cycle (before administration of the standard premedication, hydration and antiemetic agents) and 3 weeks after the 6th course. Serum creatinine was measured by the kinetic Jaffe reaction, rate blanked with color compensation on a COBAS INTEGRA 800 (Roche Diagnostics, Rotkreuz, Switzerland) with a normal range from 0.55 to 1.02 mg/dl for women [15] . Albumin (ALB) and blood urea nitrogen (BUN) concentrations were assessed by using commercial kits on the COBAS INTEGRA 800 automated analyzer with a normal range of 3.5–5 g/dl and 10–20 mg/dl, respectively. Cystatin C was measured before administration of the standard premedication, hydration and antiemetic agents, using an immunologic turbidimetric assay on the COBAS INTEGRA 800 system using Dako reagents (Dako Diagnostics, Zug, Switzerland) with a normal range from 0.63 to 1.33 mg/l. Creatinine clearance was calculated by the ClCG formula [16] : 140 years kg R GFR , 72 Cr mg/dl A W (R = coefficient of 0.85 for women; Cr = serum creatinine level; A = age; W = actual weight). GFR was calculated by the MDRD formula [3] as: GFR = 170 ! [serum Cr level (mg/dl)] –0.999 ! [age (years)] –0.176 ! 0.762 for women ! 1.18 for black women ! BUN –0.170 ! ALB 0.318 Statistical Analysis Demographic data are presented as medians or means with SD and 95% CI. Variables were compared by the Mann-Whitney test. Correlations were assessed by the parametric Pearson and nonparametric Spearman correlation tests, where appropriate. p ! 0.05 was considered to indicate statistical significance. Using a desired correlation coefficient (R) of 0.50, indicating an important relationship between cystatin C and other GFR markers with a two-sided p value of 0.05 and power of 0.85, we found the required sample size to be 32 patients [17] . Statistical calculations were performed using the Statistica for Windows version 7.0 software. D ow nl oa de d by : 54 .7 0. 40 .1 1 10 /6 /2 01 7 4: 57 :3 5 A M Bodnar et al. Kidney Blood Press Res 2010;33:360–367 362 Results Patient Characteristics Table 1 summarizes the clinical characteristics of the 34 eligible patients whose data form the basis of this report. Their median age was 54 years (range: 28–68 years). At baseline, the mean (5th–95th percentile) serum concentrations of creatinine and cystatin C were 0.66 (0.61– 0.71) mg/dl and 0.72 (0.65–0.79) mg/l, respectively. The mean GFR (5th–95th percentile) calculated by the ClCG and MDRD formulas were 106 (96–117) ml/min and 103 (94–112) ml/min/1.73 m 2 , respectively. The majority of the patients with ovarian cancer was at advanced stadium FIGO III or IV. Correlation among Measures of Renal Function Figure 1 shows that there was no relationship (p ! 0.05) between cystatin C serum concentration and the other GFR markers – serum levels of creatinine and the ClCG and MDRD formulas – before chemotherapy. After the third cycle of chemotherapy, we observed that cystatin C and GFR assessed by the MDRD formula weakly correlated (Spearman’s R = –0.36; p = 0.03). We did not see any correlation between cystatin C and serum creatinine or ClCG ( fig. 2 ). We observed a significant positive relationship between serum cystatin C and creatinine serum concentrations (Spearman’s R = 0.66; p ! 0.0001), after the 6th cycle of chemotherapy. We noted a correlation between cystatin C and serum levels of creatinine and MDRD after the 6th cycle of chemotherapy ( fig. 3 ). Serum Levels of Cystatin C and Ovarian Cancer As presented in table 2 , we found significant differences in cystatin C serum level before chemotherapy (U = 71; p = 0.004), and after the first (U = 99.5; p = 0.03) and second cycles (U = 91.5; p = 0.026) depending on the measurable residual disease shown on spiral CT scans (diameter: 1 1 cm). After the third or later cycles of chemotherapy, we did not observe any significant differencTable 1. Patient characteristics (n = 34)