Methods of Estimating Renal Function for Use in Clinical Trial Eligibility Criteria Widely Vary in Phase II and III Clinical Trials in Acute Myeloid Leukemia

Background

Renal function is an important parameter to inform drug-dosing in oncology. In acute myeloid leukemia (AML), commonly used therapies or their metabolites are renally cleared. Several equations are commonly used to estimate renal function, such as Cockcroft-Gault (CG) to estimate creatinine clearance (CrCl) and the Modification of Diet in Renal Disease (MDRD) or Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equations to calculate estimated glomerular filtration rates (eGFR). These equations frequently use endogenous serum markers, such as creatinine (Cr) and cystatin-C due to their ready availability but can have limitations. For example, Cr can be affected by muscle mass, diet, and age. Current ADDIKD international consensus guidelines recommend using the CKD-EPI creatinine formula to calculate eGFR to guide anti-cancer drug dosing unless direct GFR measurement is indicated. Renal function criteria are commonly used in clinical trial eligibility. In this study, we analyzed the types of reported renal eligibility criteria in phase II and III trials in AML and the methodology specified for renal function estimation, which can significantly impact treatment options for patients and potentially confound toxicity evaluation.

Methods

We examined the clinicaltrials.gov database to review publicly reported renal eligibility criteria for interventional phase II and III clinical trials recruiting adults with AML between 2021 to 2023. Trials including pediatric patients and exclusive phase I studies were excluded. Chi-square tests were used to evaluate for potential associations between eGFR cutoff criteria and disease variables.

Results

A total of 134 trials met criteria for review, including 84 (63%) trials specifically for AML and 50 (37%) allowing additional diagnoses. Of the total study cohort, 107 trials (80%) were evaluating chemotherapy, small molecule inhibitors, immunotherapy and/or combinations of these whereas 27 (20%) were evaluating primarily cell therapy and/or transplant-based regimens.

Among the 134 trials, 21 (16%) did not mention renal or general organ function in eligibility criteria; 16 (12%) mentioned renal or organ function in inclusion/exclusion criteria but did not specify an eGFR cutoff value; and 15 (11%) specified a serum Cr cutoff value without a specific eGFR cutoff value. Among 82 (61%) studies specifying eGFR cutoffs: 18 required eGFR ≥60 ml/min and 64 specified cutoffs between 30 ml/min to 50 ml/min or greater (table 1). We found an association between studies requiring an eGFR of 60 ml/min or greater and studies investigating cell therapy or transplant-based regimens (p<0.01). We did not find associations between eGFR cutoff requirements and trials based on disease status (relapsed/refractory AML versus other AML states, p=0.24).

We next evaluated methodologies reported in eligibility criteria to estimate renal function. Among the 113 trials commenting on renal function criteria: 15 (13%) did not report either an eGFR cutoff or methodology of determination; 67 (59%) specified eGFR cutoffs without specifying the methodology of determination and/or provided serum Cr-based cutoffs; and 31 (27%) specified either a method of direct measurement or equations to estimate eGFR (including CG-based in 25, CKD-EPI in 1, MDRD-based in 3 and radioisotope methodology in 1) (table 1). No trials mentioned cystatin-C as part of renal function determination.

Conclusion

In contemporary phase II/III clinical trials for adult patients with AML, we identified that while most trials include renal function in inclusion/exclusion criteria, there was tremendous heterogeneity in methodologies specified for determination of renal function which may make efficacy and toxicity comparisons challenging and impact patient eligibility across institutions. Several trials specified serum Cr cutoffs which can be impacted by factors besides renal function such as age or muscle mass. This study was limited by what trial criteria were publicly available and additional information specifying methodologies to calculate renal function may be available in full trial protocols. Further research is needed to determine the most suitable method for assessing eGFR in patients with AML to optimize treatment exposures for patients and to help reduce confounding of trial results or trial eligibility by institutional practice variation.