Estimating kidney function in patients with cancer: A narrative review

Aim Accurate evaluation of glomerular filtration rate (GFR) is crucial in Oncology as drug eligibility and dosing depend on estimates of GFR. However, there are no clear guidelines on the optimal method of determining kidney function in patients with cancer. We aimed to summarize the evidence on estimation of kidney function in patients with cancer. Methods We searched PubMed for literature discussing the performance of GFR estimating equations in patients with malignancy to create a table of the evidence for creatinine‐ and cystatin c‐based equations. We further reviewed novel estimation techniques such as panel eGFR, real‐time measured GFR, and functional magnetic resonance imaging. Results The commonly used GFR estimating equations were derived from populations of patients without cancer. These equations may be less applicable in Oncology due to severe sarcopenia, inflammation, and other physiologic changes in patients with cancer. The Cockcroft‐Gault equation currently dominates in clinical Oncology despite significant limitations and accumulating evidence for use of the CKD‐EPICr formula. Additional considerations in the practice of Oncology include a recently developed equation (CamGFRv2, also called the Janowitz formula) and the use of cystatin c‐based equations to overcome some of the barriers to accurate GFR estimation based on creatinine alone. Conclusion Overall, we suggest using the CKD‐EPI equations (either cystatin c or creatinine‐based) among patients with cancer in routine clinical practice and measured GFR for patients at a critical threshold for treatment decisions.