CamGFR v2: A New Model for Estimating the Glomerular Filtration Rate from Standardized or Non-standardized Creatinine in Patients with Cancer

Abstract

Purpose: Management of patients with cancer, specifically carboplatin dosing, requires accurate knowledge of glomerular filtration rate (GFR). Direct measurement of GFR is resource limited. Available models for estimated GFR (eGFR) are optimized for patients without cancer and either isotope dilution mass spectrometry (IDMS)- or non-IDMS–standardized creatinine measurements. We present an eGFR model for patients with cancer compatible with both creatinine measurement methods. Experimental Design: GFR measurements, biometrics, and IDMS- or non-IDMS–standardized creatinine values were collected for adult patients from three cancer centers. Using statistical modeling, an IDMS and non-IDMS creatinine-compatible eGFR model (CamGFR v2) was developed. Its performance was compared with that of the existing models Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Modification of Diet in Renal Disease (MDRD), Full Age Spectrum (FAS), Lund–Malmö revised, and CamGFR v1, using statistics for bias, precision, accuracy, and clinical robustness. Results: A total of 3,083 IDMS- and 4,612 non-IDMS–standardized creatinine measurements were obtained from 7,240 patients. IDMS-standardized creatinine values were lower than non-IDMS–standardized values in within-center comparisons (13.8% lower in Cambridge; P < 0.0001 and 19.3% lower in Manchester; P < 0.0001), and more consistent between centers. CamGFR v2 was the most accurate [root-mean-squared error for IDMS, 14.97 mL/minute (95% confidence interval, 13.84–16.13) and non-IDMS, 15.74 mL/minute (14.86–16.63)], most clinically robust [proportion with >20% error of calculated carboplatin dose for IDMS, 0.12 (0.09–0.14) and non-IDMS, 0.17 (0.15–0.2)], and least biased [median residual for IDMS, 0.73 mL/minute (−0.68 to 2.2) and non-IDMS, −0.43 mL/minute (−1.48 to 0.91)] eGFR model, particularly when eGFR was larger than 60 ml/minute. Conclusions: CamGFR v2 can utilize IDMS- and non-IDMS–standardized creatinine measurements and outperforms previous models. CamGFR v2 should be examined prospectively as a practice-changing standard of care for eGFR-based carboplatin dosing.

A prospective cross-sectional study estimated glomerular filtration rate from creatinine and cystatin C in adults with solid tumors

“…eGFRcr was determined from the 1976 CG, 4 2006 MDRD, 5 2009 CKD-EPI, 6 and 2020 CamGFRv2 equations. 9 eGFRcys and eGFRcr-cys were determined from the 2012 CKD-EPI equation 15 (Supplementary Table S1). eGFR was indexed for body surface area and expressed as ml/min per 1.73 m 2 .…”

“…Recent studies in patients with solid tumors have shown a potential for error in chemotherapy prescriptions using the CG equation. [7][8][9] Estimated GFR (eGFR) based on Scr (eGFRcr) using the CKD-EPI equation is recommended as the "first test" for GFR evaluation for routine clinical practice in adults. 10 Patients with cancer were not well represented in the studies in which newer eGFR equations were derived, and for several reasons, the CKD-EPI equation may be less accurate in patients with cancer than in the general population.…”

“…In 2020, a new eGFRcr equation for use with standardized Scr was developed in cancer patients (Cambridge Glomerular Filtration Rate version 2 [CamGFRv2]), but it has not been validated in an independent study population. 9 This study aimed to evaluate GFR estimating equations compared with mGFR in a large, prospective study of patients with solid tumors, using a recommended method for mGFR and standardized assays for Scr and Scys.…”

Glomerular filtration rate estimation for carboplatin dosing in patients with gynaecological cancers

“…In addition, we sought to test a novel equation (CamGFR v2) that was developed and validated recently on a large cohort of patients with cancer. 9 To our knowledge, this equation has not been previously tested in a cohort consisting of only patients with gynaecological malignancies. Using Lin's CCC, we found that among all equations evaluated, the CamGFR v2 and CG-AdBW provided the best agreement with nmGFR.…”

“…Only two have been validated in patients with cancer, the Wright formulae and the CamGFR v2 formula. 8,9 Previously, eGFR for patients with gynaecological malignancies was commonly derived using the Jelliffe equation. Subsequently, many laboratories recalibrated their creatinine assays using an isotope dilution mass spectroscopy (IDMS)-traceable reference method.…”