New Model for Estimating Glomerular Filtration Rate in Patients With Cancer

GFR Measurement and Chemotherapy Dosing in Patients with Kidney Disease and Cancer

Chemotherapeutic agents require precise dosing to ensure optimal efficacy and minimize complications. For those agents that are removed from the body by the kidney, accurate knowledge of GFR is critical. In addition, GFR needs to be determined rapidly, easily, and, if possible, with little additional cost. The ability to easily measure GFR also allows for rapid detection of nephrotoxicity. Current methodologies include direct clearance measurement of an indicator substance or estimation of creatinine clearance or GFR through regression equations that use a serum marker, such as creatinine or cystatin C. These methodologies all have shortfalls and limitations, some of which are specific to the patient with cancer. Newer methodologies that directly measure GFR are in clinical trials and offer the ability to rapidly and noninvasively provide accurate estimates of drug clearance as well as detection of nephrotoxicity. These methods offer the opportunity to refine drug dosing and improve outcomes.

Agreement and Precision Analyses of Various Estimated Glomerular Filtration Rate Formulae in Cancer Patients

The accuracy of the estimated glomerular filtration rate (eGFR) in cancer patients is very important for dose adjustments of anti-malignancy drugs to reduce toxicities and enhance therapeutic outcomes. Therefore, the performance of eGFR equations, including their bias, precision, and accuracy, was explored in patients with varying stages of chronic kidney disease (CKD) who needed anti-cancer drugs. The reference glomerular filtration rate (GFR) was assessed by the ^99mTc-diethylene triamine penta-acetic acid (^99mTc-DTPA) plasma clearance method in 320 patients and compared with the GFRs estimated by i) the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, ii) the unadjusted for body surface area (BSA) CKD-EPI equation, iii) the re-expressed Modification of Diet in Renal Disease (MDRD) study equation with the Thai racial factor, iv) the Thai eGFR equation, developed in CKD patients, v) the 2012 CKD-EPI creatinine-cystatin C, vi) the Cockcroft-Gault formula, and vii) the Janowitz and Williams equations for cancer patients. The mean reference GFR was 60.5 ± 33.4 mL/min/1.73 m². The bias (mean error) values for the estimated GFR from the CKD-EPI equation, BSA-unadjusted CKD-EPI equation, re-expressed MDRD study equation with the Thai racial factor, and Thai eGFR, 2012 CKD-EPI creatinine-cystatin-C, Cockcroft-Gault, and Janowitz and Williams equations were -2.68, 1.06, -7.70, -8.73, 13.37, 1.43, and 2.03 mL/min, respectively, the precision (standard deviation of bias) values were 6.89, 6.07, 14.02, 11.54, 20.85, 10.58, and 8.74 mL/min, respectively, and the accuracy (root-mean square error) values were 7.38, 6.15, 15.97, 14.16, 24.74, 10.66, and 8.96 mL/min, respectively. In conclusion, the estimated GFR from the BSA-unadjusted CKD-EPI equation demonstrated the least bias along with the highest precision and accuracy. Further studies on the outcomes of anti-cancer drug dose adjustments using this equation versus the current standard equation will be valuable.

Multicenter Validation of the CamGFR Model for Estimated Glomerular Filtration Rate

Important oncological management decisions rely on kidney function assessed by serum creatinine-based estimated glomerular filtration rate (eGFR). However, no large-scale multicenter comparisons of methods to determine eGFR in patients with cancer are available. To compare the performance of formulas for eGFR based on routine clinical parameters and serum creatinine not calibrated with isotope dilution mass spectrometry, we studied 3620 patients with cancer and 166 without cancer who had their glomerular filtration rate (GFR) measured with an exogenous nuclear tracer at one of seven clinical centers. The mean measured GFR was 86 mL/min. Accuracy of all models was center dependent, reflecting intercenter variability of isotope dilution mass spectrometry-creatinine measurements. CamGFR was the most accurate model for eGFR (root-mean-squared error 17.3 mL/min) followed by the Chronic Kidney Disease Epidemiology Collaboration model (root-mean-squared error 18.2 mL/min).

Estimation of Kidney Function in Oncology: Implications for Anticancer Drug Selection and Dosing

Estimation of kidney function in patients with cancer directly affects drug dosing, agent selection, and eligibility for clinical trials of novel agents. Overestimation of kidney function may lead to overdosing or inappropriate agent selection and corresponding toxicity. Conversely, underestimation of kidney function may lead to underdosing or inappropriate agent exclusion and subsequent therapeutic failure. It would seem obvious that the most accurate estimates of kidney function should be used to reduce variability in decision making and ultimately, the therapeutic outcomes of toxicity and clinical benefit. However, clinical decision making is often more complex. The Cockcroft-Gault formula remains the most universally implemented estimator of kidney function in patients with cancer, despite its relative inaccuracy compared with the Chronic Kidney Disease Epidemiology Collaboration equation. The Chronic Kidney Disease Epidemiology Collaboration equation is a more precise estimator of kidney function; however, many currently used kidney function cutoff values were determined before the development of the Chronic Kidney Disease Epidemiology Collaboration equation and creatinine assay standardization using Cockcroft-Gault estimates. There is a need for additional studies investigating the validity of currently used estimates of kidney function in patients with cancer and the applicability of traditional anticancer dosing and eligibility guidelines to modern and more accurate estimates of kidney function. In this review, we consider contemporary calculation methods used to estimate kidney function in patients with cancer. We discuss the clinical implications of using these various methods, including the potential influence on drug dosing, drug selection, and clinical trial eligibility, using carboplatin and cisplatin as case studies.

Comparing glomerular filtration rate equations and the impact of different creatinine assays on the assessment of renal function in cancer patients

BACKGROUND

Equations to estimate glomerular filtration rate based on serum creatinine are commonly used in cancer patients to assess renal function. However, there is uncertainty regarding which equation is most appropriate for this population and the impact of different creatinine assays.

METHODS

Measured isotopic glomerular filtration rate results from 120 oncology patients were used to evaluate and compare all four versions of the Wright equation, Cockcroft and Gault, Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration and the Janowitz and Williams formula; using eight different creatinine assays (five Jaffe, three enzymatic).

RESULTS

The enzymatic version of the Wright equation without creatine kinase performed better than the other versions for all eight creatinine assays. However, MDRD and Janowitz and Williams gave the best overall performance in this patient population. Performance was highly dependent on the creatinine assay used, for example, the percentage of results within 30% of the isotopic glomerular filtration rate (P30) ranged from 90.8% to 60.8% for MDRD.

CONCLUSION

The performance of any equation to estimate glomerular filtration rate is highly dependent on the creatinine assay used. Oncology units should assess the performance of glomerular filtration rate equations using their laboratory creatinine assay to determine whether they can be used safely and effectively in cancer patients.

Imprecise Kidney Function Thresholds in Cancer Clinical Trials and the Potential for Harm

Current guidance for evaluation of kidney function and drug dosing emphasize using measured or estimated glomerular filtration rate (GFR) rather than measured or estimated creatinine clearance or serum creatinine (Scr) alone. We assessed the definitions of kidney function thresholds for eligibility in cancer clinical trials. A random sample of active Phase I–III trials with cisplatin (n = 465) and studies in cancer with decreased kidney function (n = 74) were identified from clinicaltrials.gov. Among cisplatin trials, kidney function thresholds were defined by Scr alone or a composite of Scr or creatinine clearance in 46% (212/465) of studies. Only 2% (n = 11) used GFR. Among trials in participants with decreased kidney function, the proportion utilizing GFR (14%, 10/74) was modestly higher. Imprecise and logically inconsistent kidney function thresholds are in frequent use in clinical trials in cancer and may cause harm from either toxicity or impaired efficacy. We recommend the adoption and harmonization of recommended standards.

Evaluation of chronic kidney disease in cancer patients: is there a preferred estimation formula?

BACKGROUND

The evaluation of chronic kidney disease (CKD) in cancer patients seems to rely mostly on the Cockcroft-Gault (CG) formula or the creatinine levels to adjust treatment dosages which is a practice refuted by internists.

AIMS

We evaluate the overall agreement of the CG, modification of diet in renal disease (MDRD) and CKD-epidemiology collaboration equations (CKD-EPI) equation with the newly devised Janowitz and Williams' (JW) equation.

METHODS

The renal function was estimated in 235 cancer patients according to the CG, MDRD, body surface area (BSA)-adjusted MDRD, CKD-EPI, BSA-adjusted CKD-EPI and JW formulae.

RESULTS

JW equation was more in agreement with CG and CKD-EPI estimations than the other equations. Taking JW equation as reference, receiver operating characteristic curve analysis showed that CG eGFR had the higher area under the curve when compared with other equations. Hierarchical cluster analysis showed more proximity between CG and JW equations than the other equations.

CONCLUSION

The newly proposed JW eGFR estimation was more in agreement with CG equation than the other equations.

Variability of carboplatin dose calculation methods in Spain

OBJECTIVE

To describe and analyze the variability in carboplatin dosing strategies in Spanish hospitals.

METHODS

We designed a questionnaire consisting of 19 multiple-choice items structured in two sections (hospital characteristics and carboplatin dosing data). The questionnaire was sent by e-mail to all the oncology pharmacists included in the register of the Spanish Oncology Pharmacy Group (GEDEFO), and we analyzed the completed questionnaires.

RESULTS

Response rate was 33.5% from a total of 185 pharmacy services invited to take part in the survey. All hospitals used the Calvert formula to calculate carboplatin dose with glomerular filtration rate estimated by a formula, most commonly the Cockcroft-Gault equation (80.7%). Carboplatin doses were capped in most hospitals (91.9%): 54.8% capped creatinine clearance at 125 mL/min, 11.3% capped serum creatinine, and 19.3% capped both creatinine clearance and serum creatinine. Serum creatinine cut-off values ranged from 0.36 mg/dL to 1 mg/dL. The most commonly used body weight was actual body weight for underweight, normal weight, and overweight patients. The use of adjusted ideal body weight increased in obese and especially in morbidly obese patients.

CONCLUSION

The results from this survey show the variability that exists in carboplatin dose calculation methods among Spanish hospitals and the need to continue investigating to find the optimum dose calculation method and unify criteria to avoid differences between sites that can affect effectiveness and toxicity of carboplatin-containing treatments.

GFR estimation in lenalidomide treatment of multiple myeloma patients: a prospective cohort study

BACKGROUND

The estimated glomerular filtration rate (eGFR) is clinically used to approximate renal function and adapt drug dosage. Multiple myeloma is a hematological disease; its prognosis is largely influenced by renal function. We evaluated two commonly used GFR estimations, CKD-EPI and MDRD (CKD Epidemiology Collaboration; Modification of Diet in Renal Disease) in myeloma patients undergoing treatment with lenalidomide, a renally excreted immunomodulatory drug.

METHODS

We prospectively studied 130 myeloma patients receiving lenalidomide treatment at our institution. At baseline and after 3 months, GFR estimations were performed based on the CKD-EPI and MDRD equations. We compared eGFR-dependent CKD staging and lenalidomide dosage assignments.

RESULTS

Initially, most patients were classified as CKD stage I/II, using both equations. Comparison of baseline renal function via CKD-EPI and MDRD induced concordance of CKD staging in 83% of patients, while CKD-EPI improved CKD staging in 16% of patients (p = 0.11). CKD-EPI assigned 3% of patients to higher lenalidomide dosing as opposed to MDRD. Both equations showed improved eGFR after 3 months of lenalidomide treatment.

CONCLUSIONS

In our multiple myeloma patient cohort, CKD-EPI and MDRD led to similar CKD staging with minor differences in lenalidomide dosage assignment. Consistent with previous studies, eGFR improved under lenalidomide treatment. To standardize GFR estimation in myeloma patients, we suggest using the CKD-EPI equation.

Outcome Measures Used to Report Kidney Function in Studies Investigating Surgical Management of Kidney Tumours: A Systematic Review

CONTEXT

Most practice decisions relevant to preserving kidney function in patients managed surgically for kidney tumours are driven by observational studies. A wide range of outcome measures are used in these studies, which reduces comparability and increases the risk of reporting bias.

OBJECTIVE

To comprehensively and succinctly describe the outcomes used to evaluate kidney function in studies evaluating surgical management of kidney tumours.

EVIDENCE ACQUISITION

Electronic search of the PubMed database was conducted to identify studies with at least one measure of kidney function in patients managed surgically for kidney tumours, published between January 2000 and September 2017. Abstracts were initially screened for eligibility. Full texts of articles were then evaluated in more detail for inclusion. A narrative synthesis of the evidence was conducted.

EVIDENCE SYNTHESIS

A total of 312 studies, involving 127905 participants, were included in this review. Most were retrospective (n=274) studies and conducted in a single centre (n=264). Overall, 78 unique outcome measures were identified, which were grouped into six outcome categories. Absolute postoperative kidney function (n=187), relative kidney function (n=181), and postoperative chronic kidney disease (n=131) were most frequently reported. Kidney function was predominantly quantified using estimated glomerular filtration rate or creatinine clearance (n=255), most using the modification of diet in renal disease equation (n=182). Only 70 studies provided rationale for specific outcome measures used.

CONCLUSIONS

There is significant variability in the reporting and quantification of kidney function in studies evaluating patients managed surgically for kidney tumours. A standardised approach to measuring and reporting kidney function will increase the effectiveness of outcomes reported and improve relevance of research findings within a clinical context.

PATIENT SUMMARY

Although we know that the removal of a kidney can reduce kidney function, clinical significance of various approaches is a matter of debate. This article demonstrates significant variability in the way kidney function was reported across all studies of patients with kidney cancer undergoing surgery, indicating a need for standardisation.

Pragmatic Use of Kidney Function Estimates for Drug Dosing: The Tide Is Turning

Creatinine clearance has been the most common method of estimating kidney function for the purpose of drug dosing for decades. The availability and extensive clinical use of estimated glomerular filtration rate (eGFR) now provides clinicians a potential alternative. Currently, data demonstrating the validity of eGFR-based drug dosing is limited, but proof of principle has been established and the tide related to use of eGFR for drug dosing appears to be turning. Use of the same kidney function estimate for management of kidney disease, drug development and dosing, and harmonization in all clinical arenas would be ideal. Use of multiple equations can lead to differences in kidney function estimates and corresponding drug dosing regimens, which necessitates clinical judgment and a pragmatic approach when rendering drug dosing decisions. Careful consideration of the risk-benefit ratio of individual drugs and dosing regimens within each patient is warranted. Going forward, FDA guidance will likely incentivize pharmaceutical manufacturers to generate eGFR-based dosing recommendations in addition to creatinine clearance for inclusion in the label of newly approved drugs. However, dosing information for currently approved drugs will continue to be based on creatinine clearance alone, so clinicians must be vigilant in the assessment of kidney function in order to provide optimal pharmacotherapy.

Assessment of Kidney Function in Patients With Cancer

Cancer patients are living longer. The sequelae of cancer treatment and the role of comorbid conditions present before the diagnosis, such as CKD, have been increasingly recognized. The interface between CKD and cancer is multifaceted. CKD is frequently observed in patients with cancer, and cancer treatment contributes to CKD development and progression. In addition, CKD has been recognized as an important risk factor for cancer development and reduced specific cancer survival. In this context, an accurate evaluation of the glomerular filtration rate (GFR) during oncologic treatment is pivotal and is used to define surgery strategies, program prophylactic management of contrasted examinations, make decisions on cisplatin eligibility, and adjust drug prescriptions, particularly chemotherapy agents. Although the most commonly used equations to estimate GFR based on serum creatinine levels in clinical practice (Cockcroft-Gault, Modification of Diet in Renal Disease Study, and CKD Epidemiology Collaboration equations) have not been validated in patients with cancer in large prospective studies, there is increasingly evidence supporting the use of CKD Epidemiology Collaboration equation to assess the GFR in patients with cancer, including for the use of chemotherapy prescriptions. Many patients with cancer may have changes in nutrition status and clearance measurements such as exogenous filtration markers might be extremely useful when clinical decisions differ depending on the GFR level. Future perspectives include the advent of new serum GFR biomarkers such as cystatin C, beta-trace protein, and beta-2 microglobulin as well as the GFR assessment by measuring total kidney parenchymal volume through image examinations.