Estimating kidney function in patients with cancer: A narrative review

Comparison of GFR estimation equations using creatinine, cystatin C, and their combination in pediatric hematology-oncology: no single equation is superior across subgroups

BACKGROUND

Accurate assessment of renal function is essential in treating pediatric patients dosed with nephrotoxic chemotherapy. The validity of the bedside Schwartz, 5-covariate St. Jude (5SJ), CKiD-CysC-U25, combined Cr-CysC-based CysPed, and the serum creatinine-BUN-cystatin C-based CKiD (CKiD Cr-CysC) equations were evaluated in pediatric hematology and oncology patients.

METHODS

A retrospective analysis was conducted comparing estimated glomerular filtration rate (eGFR) to measured GFR (mGFR) obtained from technetium- 99 m diethylenetriaminepentaacetic acid (99 mTc-DTPA) clearance between January 2016 and May 2022. The influence of corticosteroid use and inflammation in our patient population was evaluated for effect on serum cystatin C (CysC) concentrations and mGFR.

RESULTS

All equations agreed within 2 SD of the mean difference with mGFR, but the 5SJ equation had the smallest bias followed closely by the CysPed equation. Overall accuracy (P30) was assessed, and the 5SJ, CKiD Cr-CysC, CysPed, and CKiD-Cys-U25 exhibited comparable performance. In our patient population, we did not observe an effect of corticosteroids (cumulative dosage of > 0.5 mg/kg within the past 14 days) or the presence of inflammation (CRP > 1.2 mg/L) on cystatin C concentrations or mGFR.

CONCLUSIONS

In our pediatric hematology and oncology patient population, no one estimating equation demonstrated superior accuracy and bias overall and in all subgroups. Neither corticosteroid use nor elevated CRP influenced serum CysC concentrations or eGFR.

A Bayesian Framework for Optimizing Amikacin Therapy in Critically Ill Patients With Cancer

BACKGROUND

Amikacin (AMK) is used to treat gram-negative bacterial infections in intensive care unit (ICU) patients. However, its narrow therapeutic range and high interindividual variability can lead to toxicity and ineffectiveness. This study aimed to establish a roadmap for AMK therapeutic drug monitoring in critically ill patients with cancer to provide a Bayesian estimator of bedside applicability.

METHODS

An observational retrospective study was conducted on oncological patients admitted to the ICU, treated with AMK as a 30-min intravenous infusion at 5.8-39.2 mg/kg. The plasma concentrations were analyzed using a nonlinear mixed-effects modeling approach. Covariate analyses were performed using anthropometric and laboratory data, concomitant drugs, and comorbidities. The model predictive performance was compared with previous AMK dosing approaches using the Bland-Altman method.

RESULTS

The concentration-time profiles were best described using a one-compartment model with linear elimination. The estimated glomerular filtration rate was a significant covariate of clearance (CL), explaining 16% of the interpatient variability. Body weight was positively correlated with the volume of distribution, accounting for 4% of the variability. Our model reduced the bias in the estimates of individual CL values compared with that of other available methods and was further implemented in DoseMeRx for real-time application at the bedside.

CONCLUSIONS

This study provides an effective example of a Bayesian estimation method for individualizing AMK doses in critically ill patients with cancer. Collecting more comprehensive patient information, including additional biomarkers for renal function, could further refine the model and improve its predictive performance in this special population.

Glomerular Filtration Rate (GFR) Estimation with Cystatin C-Past, Present, and Future

BACKGROUND

Cystatin C is a long-established filtration marker which can be used to assess kidney function, but it has been sparingly used for clinical care due to creatinine's role as the primary biomarker for kidney function assessment based on estimated glomerular filtration rate (eGFR).

CONTENT

This review summarizes the evolution of cystatin C's role in kidney disease assessment and highlights new guidelines promoting more widespread use. Specifically, the 2021 National Kidney Foundation and American Society of Nephrology Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease report, and the 2024 Kidney Disease Improving Global Outcomes (KDIGO) Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (CKD), recommend increased use of cystatin C as an alternative and complementary biomarker for kidney function assessment, since it does not differ by race like creatinine, correlates better with adverse outcomes compared to creatinine, and provides a more accurate eGFR when used in combination with creatinine.

SUMMARY

While robust literature demonstrates improved accuracy with cystatin C-based eGFR (eGFRcys) in certain clinical subpopulations, future research is needed to better understand its performance relative to creatinine-based eGFR (eGFRcr) and measured glomerular filtration rate (mGFR) in additional diverse cohorts, and to achieve assay standardization to match the performance of creatinine assays. Additionally, cystatin C testing availability will need to be broadened from primarily reference laboratories to local laboratories, and partnerships will need to be developed between clinical stakeholders and the laboratory to promote cystatin C's clinical use, to achieve widespread adoption of guideline-recommended eGFR equations.

Noval insights and therapeutic strategies for tumor-induced kidney pathologies

Recent progress in elucidating the role of specific antidiuretic hormones in Drosophila models has provided valuable insights into the mechanisms underlying tumor-induced renal dysfunction. Xu et al. identified the mammalian neurokinin 3 receptor (TACR3), a homolog of the G protein-coupled receptor TkR99D in fruit flies, as a potential therapeutic target for alleviating renal tubular dysfunction in mice with malignant neoplasms. Here, we commented on these findings by emphasizing the structural and evolutionary significance of TACR3 and provided an in-depth analysis of cell type specific expression of TACR3 in response to renal injury and expressional dynamics during renal carcinoma progression. The implications of these findings for transforming the therapeutic approaches to renal complications associated with oncological disorders were highlighted. We also acknowledged the limitations of current experimental models in this study and emphasized the necessary clinical validation in the future. These insights could contribute to the advancement of diagnostic and therapeutic strategies for treating tumor-related renal pathologies.

Drug stewardship in chronic kidney disease to achieve effective and safe medication use

People living with chronic kidney disease (CKD) often experience multimorbidity and require polypharmacy. Kidney dysfunction can also alter the pharmacokinetics and pharmacodynamics of medications, which can modify their risks and benefits; the extent of these changes is not well understood for all situations or medications. The principle of drug stewardship is aimed at maximizing medication safety and effectiveness in a population of patients through a variety of processes including medication reconciliation, medication selection, dose adjustment, monitoring for effectiveness and safety, and discontinuation (deprescribing) when no longer necessary. This Review is aimed at serving as a resource for achieving optimal drug stewardship for patients with CKD. We describe special considerations for medication use during pregnancy and lactation, during acute illness and in patients with cancer, as well as guidance for the responsible use of over-the-counter drugs, herbal remedies, supplements and sick-day rules. We also highlight inequities in medication access worldwide and suggest policies to improve access to quality and essential medications for all persons with CKD. Further strategies to promote drug stewardship include patient education and engagement, the use of digital health tools, shared decision-making and collaboration within interdisciplinary teams. Throughout, we position the person with CKD at the centre of all drug stewardship efforts.