Correlation of Cystatin-C and radionuclidic measurement method of glomerular filtration rate in patients with lung cancer receiving cisplatin treatment

The Current State of Nuclear Nephrology in Modern Medicine

Glomerular filtration rate (GFR) is the most reliable parameter of renal function. Regarding the complexity of the gold standard inulin clearance, different estimating equations have been developed with CKD-EPI creatinine equation recommended as the most reliable one. In some clinical situations where creatinine based equations might not be valid, alternative methods are needed. Nuclear medicine methods for measuring GFR with 51Cr EDTA and 99mTc DTPA have been widely used for decades. There are different methodologies for the measurement of kidney function with radiopharmaceuticals: urinary clearance, plasma clearance, multiple plasma sampling, slope intercept, single sample plasma equation, slope only, and the gamma camera-based method. Greater precision of measuring GFR is needed in certain clinical situations. The most common are diagnosis and follow up of chronic kidney disease and definition of the beginning of replacement therapy. The assessment of renal function is also important for potential kidney donors. In recent years, with the introduction of new chemotherapeutic drugs and targeted therapy, oncologic patients treated with nephrotoxic drugs have become more commonly referred for measuring GFR. The monitoring of renal function is important during treatment in order to detect the transformation from reversible acute kidney injury to irreversible chronic kidney disease as well as in the cases of renal insufficiency reduce the dosage and prevent accumulation of the drug and avoid dosage related toxic effects. Assessment of kidney function using measured mGFR will be an important milestone in the creation of more accurate and expanding personalized medicine principle in current onconephrology practice.

Medication-Related Adverse Events and Discordancies in Cystatin C-Based vs Serum Creatinine-Based Estimated Glomerular Filtration Rate in Patients With Cancer

Importance

Serum creatinine-based estimated glomerular filtration rate (eGFRcr) may overestimate the glomerular filtration rate (GFR) in patients with cancer. Cystatin C-based eGFR (eGFRcys) is an alternative marker of GFR.

Objective

To determine whether the therapeutic drug levels and adverse events (AEs) associated with renally cleared medications were higher in patients with cancer whose eGFRcys was more than 30% lower than their eGFRcr.

Design, Setting, and Participants

This cohort study analyzed adult patients with cancer at 2 major academic cancer centers in Boston, Massachusetts. These patients had their creatinine and cystatin C measured on the same day between May 2010 and January 2022. The date of the first simultaneous eGFRcr and eGFRcys measurement was considered to be the baseline date.

Exposure

The primary exposure was eGFR discordance, defined as an eGFRcys that was more than 30% lower than the eGFRcr.

Main Outcomes and Measures

The primary outcome was risk of the following medication-related AEs within 90 days of the baseline date: (1) supratherapeutic vancomycin trough level greater than 30 μg/mL, (2) trimethoprim-sulfamethoxazole-related hyperkalemia (>5.5 mEq/L), (3) baclofen toxic effect, and (4) supratherapeutic digoxin level (>2.0 ng/mL). For the secondary outcome, a multivariable Cox proportional hazards regression model was used to compare 30-day survival of those with vs without eGFR discordance.

Results

A total of 1869 adult patients with cancer (mean [SD] age, 66 [14] years; 948 males [51%]) had simultaneous eGFRcys and eGFRcr measurement. There were 543 patients (29%) with an eGFRcys that was more than 30% lower than their eGFRcr. Patients with an eGFRcys that was more than 30% lower than their eGFRcr were more likely to experience medication-related AEs compared with patients with concordant eGFRs (defined as eGFRcys within 30% of eGFRcr), including vancomycin levels greater than 30 μg/mL (43 of 179 [24%] vs 7 of 77 [9%]; P = .01), trimethoprim-sulfamethoxazole-related hyperkalemia (29 of 129 [22%] vs 11 of 92 [12%]; P = .07), baclofen toxic effects (5 of 19 [26%] vs 0 of 11; P = .19), and supratherapeutic digoxin levels (7 of 24 [29%] vs 0 of 10; P = .08). The adjusted odds ratio for vancomycin levels more than 30 μg/mL was 2.59 (95% CI, 1.08-7.03; P = .04). Patients with an eGFRcys more than 30% lower than their eGFRcr had an increased 30-day mortality (adjusted hazard ratio, 1.98; 95% CI, 1.26-3.11; P = .003).

Conclusions and relevance

Results of this study suggest that among patients with cancer with simultaneous assessment of eGFRcys and eGFRcr, supratherapeutic drug levels and medication-related AEs occurred more commonly in those with an eGFRcys more than 30% lower than their eGFRcr. Future prospective studies are needed to improve and personalize GFR estimation and medication dosing in patients with cancer.

Medication-related adverse events in patients with cancer and discrepancies in cystatin C- versus creatinine-based eGFR

Background

Creatinine-based estimated glomerular filtration rate (eGFRCRE) may overestimate kidney function in patients with cancer. Cystatin C-based eGFR (eGFRCYS) is an alternative marker of kidney function. We investigated whether patients with an eGFR discrepancy, defined as eGFRCYS >30% lower than the concurrent eGFRCRE, had an increased risk of adverse events resulting from renally-cleared medications.

Patients and Methods

We conducted a cohort study of adult patients with cancer who had serum creatinine and cystatin C measured on the same day between May 2010 and January 2022 at two academic cancer centers in Boston, MA. The primary outcome was the incidence of each of the following medication-related adverse events: 1) supratherapeutic vancomycin levels (>30μg/mL); 2) trimethoprim-sulfamethoxazole-related hyperkalemia (>5.5mEq/L); 3) baclofen-induced neurotoxicity; and 4) supratherapeutic digoxin levels (>2.0ng/mL).

Results

1988 patients with cancer had simultaneous eGFRCYS and eGFRCRE. The mean age was 66 years (SD±14), 965 (49%) were female, and 1555 (78%) were non-Hispanic white. eGFR discrepancy occurred in 579 patients (29%). Patients with eGFR discrepancy were more likely to experience medication-related adverse events compared to those without eGFR discrepancy: vancomycin levels >30μg/mL (24% vs. 10%, p=0.004), trimethoprim- sulfamethoxazole-related hyperkalemia (24% vs. 12%, p=0.013), baclofen-induced neurotoxicity (25% vs. 0%, p=0.13), and supratherapeutic digoxin levels (38% vs. 0%, p=0.03). The adjusted OR for vancomycin levels >30μg/mL was 2.30 (95% CI 1.05 - 5.51, p = 0.047).

Conclusion

Among patients with cancer with simultaneous assessment of eGFRCYS and eGFRCRE, medication-related adverse events occur more commonly in those with eGFR discrepancy. These findings underscore the importance of accurate assessment of kidney function and appropriate dosing of renally-cleared medications in patients with cancer.

Role of cystatin C in urogenital malignancy

Urogenital malignancy accounts for one of the major causes of cancer-related deaths globally. Numerous studies have investigated novel molecular markers in the blood circulation, tumor tissue, or urine in order to assist in the clinical identification of tumors at early stages, predict the response of therapeutic strategies, and give accurate prognosis assessment. As an endogenous inhibitor of lysosomal cysteine proteinases, cystatin C plays an integral role in diverse processes. A substantial number of studies have indicated that it may be such a potential promising biomarker. Therefore, this review was intended to provide a detailed overview of the role of cystatin C in urogenital malignancy.

Assessment of kidney function: clinical indications for measured GFR

In the vast majority of cases, glomerular filtration rate (GFR) is estimated using serum creatinine, which is highly influenced by age, sex, muscle mass, body composition, severe chronic illness and many other factors. This often leads to misclassification of patients or potentially puts patients at risk for inappropriate clinical decisions. Possible solutions are the use of cystatin C as an alternative endogenous marker or performing direct measurement of GFR using an exogenous marker such as iohexol. The purpose of this review is to highlight clinical scenarios and conditions such as extreme body composition, Black race, disagreement between creatinine- and cystatin C-based estimated GFR (eGFR), drug dosing, liver cirrhosis, advanced chronic kidney disease and the transition to kidney replacement therapy, non-kidney solid organ transplant recipients and living kidney donors where creatinine-based GFR estimation may be invalid. In contrast to the majority of literature on measured GFR (mGFR), this review does not include aspects of mGFR for research or public health settings but aims to reach practicing clinicians and raise their understanding of the substantial limitations of creatinine. While including cystatin C as a renal biomarker in GFR estimating equations has been shown to increase the accuracy of the GFR estimate, there are also limitations to eGFR based on cystatin C alone or the combination of creatinine and cystatin C in the clinical scenarios described above that can be overcome by measuring GFR with an exogenous marker. We acknowledge that mGFR is not readily available in many centres but hope that this review will highlight and promote the expansion of kidney function diagnostics using standardized mGFR procedures as an important milestone towards more accurate and personalized medicine.

Biomarkers of Drug-Induced Kidney Toxicity

Blood urea nitrogen and serum creatinine are imperfect markers of kidney function because they are influenced by many renal and nonrenal factors independent of kidney function. A biomarker that is released directly into the blood or urine by the kidney in response to injury may be a better early marker of drug-induced kidney toxicity than blood urea nitrogen and serum creatinine. Urine albumin and urine protein, as well as urinary markers kidney injury molecule-1 (KIM-1), β2-microglobulin (B2M), cystatin C, clusterin, and trefoil factor-3 (TFF-3) have been accepted by the Food and Drug Administration and European Medicines Agency as highly sensitive and specific urinary biomarkers to monitor drug-induced kidney injury in preclinical studies and on a case-by-case basis in clinical trials. Other biomarkers of drug-induced kidney toxicity that have been detected in the urine of rodents or patients include IL-18, neutrophil gelatinase-associated lipocalin, netrin-1, liver-type fatty acid-binding protein (L-FABP), urinary exosomes, and TIMP2 (insulin-like growth factor-binding protein 7)/IGFBP7 (insulin-like growth factor-binding protein 7), also known as NephroCheck, the first Food and Drug Administration-approved biomarker testing platform to detect acute kidney injury in patients. In the future, a combined use of functional and damage markers may advance the field of biomarkers of drug-induced kidney toxicity. Earlier detection of drug-induced kidney toxicity with a kidney-specific biomarker may result in the avoidance of nephrotoxic agents in clinical studies and may allow for earlier intervention to repair damaged kidneys.

The value of serum cystatin C in early evaluation of renal insufficiency in patients undergoing chemotherapy: a systematic review and meta-analysis

PURPOSE

Several studies have shown that cystatin C levels can be used to detect decline in renal function in cancer patients receiving chemotherapy, and can serve as a supplement to creatinine level measurement for early detection of renal insufficiency. Nevertheless, use of the parameter remains controversial. This study aimed to assess the value of serum cystatin C levels in evaluation of early renal insufficiency due to chemotherapy.

METHODS

Studies were retrieved from PubMed, Ovid Embase, the Web of Science, the Cochrane Library, Ovid, and the CNKI databases up to May 15, 2018. Serum levels of cystatin C before and after chemotherapy were evaluated for its ability to assess renal function.

RESULTS

A total of 12 studies, including 1775 participants, met our inclusion and exclusion criteria. Pooled analysis revealed that the levels of serum cystatin C in cancer patients after chemotherapy were significantly higher than those of patients prior to treatment [standard mean difference (SMD) = 0.54, 95% CI 0.34-0.74, P = 0.0000]. Compared to creatinine, serum cystatin C increased significantly in the early phases of glomerular filtration rate (GFR) change before and after chemotherapy (GFR ≥ 90 ml/min/1.73 m², P < 0.05 vs. P > 0.05, 5.83%; 60 < GFR < 90 ml/min/1.73 m², P < 0.01 vs. P > 0.01, 38.83%) and increased more substantially in the later phases (GFR < 60 ml/min/1.73 m², P < 0.01 vs. P < 0.01, 70.87% vs. 23.09%). However, creatinine decreased even in the early phases and did not increase in an obvious manner until the later phases (GFR < 60 ml/min/1.73 m², P < 0.01, 23.09%). The GFR values were derived from measured methods.

CONCLUSIONS

Cystatin C may be superior to creatinine for the detection of minor changes in GFR in early stages of renal insufficiency secondary to chemotherapy. More studies are needed to further verify this result.

Educational review: measurement of GFR in special populations

IMPORTANCE

Changes in kidney function are typically followed by the sequential estimation of glomerular filtration rate (eGFR). Formulae for eGFR work well on a population basis, but there are well-known conditions where they do not work.

OBJECTIVE

The purpose of this review is to summarize the existing literature on special populations in the pediatric age range and provide recommendations on how to estimate GFR in these populations.

FINDINGS

The reliability of creatinine depends on muscle mass, while cystatin C (not widely available) is limited by inflammation and changes in protein catabolism. Various dietary factors can alter eGFR. Renal function in neonates changes drastically every day, and there are currently no satisfactory reference intervals for routine pediatric use. Gender effects and conditions such as wasting disease and obesity require alternative ways to obtain eGFR. In oncology patients, chemotherapy may negatively affect renal function, and nuclear GFR measurements may be necessary. For body builders, high muscle mass may lead to underestimation of eGFR using creatinine.

CONCLUSIONS AND RELEVANCE

Clinicians should be aware of special populations that may yield misleading eGFRs with conventional creatinine-based formulae, and that the alternative methods may be more appropriate for some populations.

Possible risk of overestimation of renal function using cystatin C-based eGFR in testicular cancer survivors treated with cisplatin-based chemotherapy

BACKGROUND

Chronic kidney disease (CKD) is a major long-term morbidity of testicular cancer (TC) survivors cured by cisplatin-based chemotherapy. We conducted the present study to elucidate the usefulness of cystatin-based estimated glomerular filtration rates (eGFRcys) for diagnosis of CKD compared to creatinine-based eGFR (eGFRcreat) in those patients.

METHODS

eGFRcys and eGFRcreat were measured in 53 TC survivors. The 24-h creatinine clearance (CrCl) was measured in 12 TC survivors and 17 CKD patients with medical disease; all of them had eGFRcreat <60 m/min/1.73 m². Also, urinary beta2-microglobulin and albumin concentrations in spot urine specimens were measured.

RESULTS

The mean eGFRcreat was significantly lower than eGFRcys, at 67.9 and 95.2 ml/min/1.73 m², respectively (p < 0.05). The prevalence of stage 3-5 CKD differed by GFR estimation methods. It was 47.2% with eGFRcreat and only 7.5% with eGFRcys. There were 21 patients with eGFRcreat <60 ml/min/1.73 m² and eGFRcys ≥60 ml/min/1.73 m². In all 12 TC survivors, the eGFRcys values were higher than both eGFRcreat and GFR (24-h CrCl). In contrast, no difference was observed among eGFR values in the 17 patients with CKD due to medical disease. Ten of 21 patients with eGFRcreat <60 ml/min/1.73 m² and eGFRcys ≥60 ml/min/1.73 m² showed significant beta2-microglobulinuria: a higher prevalence than that in patients with both eGFRs ≥60 ml/min/1.73 m². Also, the incidence of microalbuminuria tended to be high in those patients.

CONCLUSIONS

The present study suggests that eGFRcys may overestimate renal function in TC survivors cured by cisplatin-based chemotherapy.

Changes in blood concentrations of trace metals in cancer patients receiving cisplatin-based chemotherapy

The administration of cisplatin (CDDP) may influence trace metal concentrations in body fluids. In order to test this hypothesis, the blood concentrations of trace metals were determined during the present study in eight Japanese esophageal and lung cancer patients receiving CDDP-based chemotherapy. The levels of manganese, iron (Fe), cobalt, copper, zinc (Zn), platinum and lead in the plasma were determined by inductively coupled plasma-mass spectrometry. In addition, the serum levels of Fe, transferrin and ferritin were evaluated. The baseline plasma concentration of Fe in patients with esophageal cancer was significantly lower than that in lung cancer patients (P=0.011), although there were no significant differences identified with respect to the plasma levels of other trace metals. The data obtained from six fasting patients without blood transfusion demonstrated that plasma concentrations of Fe increased 3.5-fold soon after CDDP treatment and returned to baseline levels ~10 days after therapy. The excessive Fe levels in the bloodstream induced changes in serum ferritin and transferrin levels. Furthermore, serum Zn levels increased 1.8-fold in the 1-3 days following CDDP treatment, and serum cystatin C levels transiently increased. These findings indicate that serum Fe and Zn levels may be useful to understanding the physiological responses in the early stages of CDDP-based chemotherapy, which may be associated with systemic inflammation and/or tissue distribution of CDDP.

Cystatin C Based Equation Accurately Estimates Glomerular Filtration Rate in Children With Solid and Central Nervous System Tumours: Enough Evidence to Change Practice?

BACKGROUND

Assessing the glomerular filtration rate (GFR) of paediatric patients receiving nephrotoxic chemotherapy is a vital element of clinical practice. Isotopically measured GFR is the gold standard in terms of accuracy but requires injection of tracer followed by several hours of blood tests. Estimation of GFR using creatinine is widely used but inaccurate, and there is increasing concern regarding its usage for paediatric oncology patients. Cystatin C (CysC) based equations are increasingly used in other paediatric specialities to estimate GFR, and their usefulness in paediatric oncology practice is becoming evident.

METHODS

We assessed the renal function of children with solid tumours and CNS tumours receiving nephrotoxic chemotherapy over a 1-year period using paired CysC and isotopic GFR.

RESULTS

Fifty-six sets of measurements were reviewed with estimated GFR predicted using CysC-based and creatinine-based equations. The best performing equation was the 'new CKiD' equation, which estimated GFR within 30% of the measured GFR on 86% of occasions, outperforming the Schwartz equation. If estimated GFR using this equation was >100 ml/min/1.73 m(2) , all values of measured GFR were normal at >90 ml/min/1.73 m(2) , a category containing two-thirds of all measurements.

CONCLUSIONS

The new CKiD equation predicts GFR in paediatric oncology patients with more accuracy than creatinine-based equations. When the estimated GFR is >100 ml/min/1.73 m(2) , isotopic GFR can be safely omitted.

Measurement of glomerular filtration rate by dynamic contrast-enhanced magnetic resonance imaging using a subject-specific two-compartment model

Measuring glomerular filtration rate (GFR) by dynamic contrast‐enhanced (DCE) magnetic resonance imaging (MRI) as part of standard of care clinical MRI exams (e.g., in pediatric solid tumor patients) has the potential to reduce diagnostic burden. However, enthusiasm for this relatively new GFR test may be curbed by the limited amount of cross‐calibration studies with reference GFR techniques and the vast variety of MR tracer model algorithms causing confusion on the choice of model. To advance MRI‐based GFR quantification via improved GFR modeling and comparison with associated ^99mTc‐DTPA‐GFR, 29 long‐term Wilms' tumor survivors (19.0–43.3 years, [median 32.0 ± 6.0 years]) treated with nephrectomy, nonnephrotoxic chemotherapy ± radiotherapy underwent MRI with Gd‐DTPA administration and a ^99mTc‐DTPA GFR test. For DCE‐MRI‐based GFR estimation, a subject‐specific two‐compartment (SS‐2C) model was developed that uses individual hematocrit values, automatically defines subject‐specific uptake intervals, and fits tracer‐uptake curves by incorporating these measures. The association between reference ^99mTc‐DTPA GFR and MR‐GFRs obtained by SS‐2C, three published 2C uptake, and inflow–outflow models was investigated via linear regression analysis. Uptake intervals varied from 64 sec to 141 sec [96 sec ± 21 sec] and hematocrit values ranged from 30% to 49% [41% ± 4%]; these parameters can therefore not be assumed as constants in 2C modeling. Our MR‐GFR estimates using the SS‐2C model showed accordingly the highest correlation with ^99mTc‐DTPA‐GFRs (R² = 0.76, P < 0.001) compared with other models (R²‐range: 0.36–0.66). In conclusion, SS‐2C modeling of DCE‐MRI data improved the association between GFR obtained by ^99mTc‐DTPA and Gd‐DTPA DCE‐MRI to such a degree that this approach could turn into a viable, diagnostic GFR assay without radiation exposure to the patient.

Cystatin C is a disease-associated protein subject to multiple regulation

A protease inhibitor, cystatin C (Cst C), is a secreted cysteine protease inhibitor abundantly expressed in body fluids. Clinically, it is mostly used to measure glomerular filtration rate as a marker for kidney function due to its relatively small molecular weight and easy detection. However, recent findings suggest that Cst C is regulated at both transcriptional and post‐translational levels, and Cst C production from haematopoietic cell lineages contributes significantly to the systematic pools of Cst C. Furthermore, Cst C is directly linked to many pathologic processes through various mechanisms. Thus fluctuation of Cst C levels might have serious clinical implications rather than a mere reflection of kidney functions. Here, we summarize the pathophysiological roles of Cst C dependent and independent on its inhibition of proteases, outline its change of expression by various stimuli, and elucidate the regulatory mechanisms to control this disease‐related protease inhibitor. Finally, we discuss the clinical implications of these findings for translational gains.