Sarcopenia, adiposity, and discrepancies in cystatin C versus creatinine-based eGFR in patients with cancer: a cross-sectional study

PurposeCreatinine-based estimated glomerular filtration rate (eGFRCRE) may overestimate kidney function in patients with sarcopenia. While Cystatin C-based eGFR (eGFRCYS) is less affected by muscle mass, it may underestimate kidney function in patients with obesity. We sought to evaluate the relationship between body composition and discrepancies between creatinine and eGFRCRE and eGFRCYS in patients with cancer. MethodsWe conducted a cross-sectional study of consecutive adults with cancer who had an abdominal CT scan performed within 90 days of simultaneous eGFRCRE and eGFRCYS measurements between May 2010-January 2022. Sarcopenia was defined using independent sex-specific cutoffs for skeletal muscle index (SMI) at the level of the third lumbar vertebral body (<39 cm2/m2 for women,<55 cm2/m2 for men). High adiposity was defined as the highest sex-specific quartile of total (visceral plus subcutaneous) adiposity index in the cohort. The primary outcome was eGFR discrepancy, defined by eGFRCYS >30% lower than eGFRCRE. We estimated the odds of eGFR discrepancy using multivariable logistic regression modeling. ResultsOf 545 included patients (mean age 63 {+/-}14 years, 300 [55%] females, 440 [80.7%] non-Hispanic white), 320 (58.7%) met the criteria for sarcopenia and 136 (25%) had high adiposity. After adjustment for potential confounders, sarcopenia and high adiposity were both associated with >30% eGFR discrepancy (adjusted odds ratio [aOR] 1.90, 95% confidence interval [CI] 1.12-3.24; aOR 2.01, 95% CI 1.15-3.52, respectively). ConclusionDiscrepancies in eGFRCRE and eGFRCYS are common in adult patients with cancer, and sarcopenia and high adiposity are both independently associated with large eGFR discrepancies. Significance statementSerum creatinine may overestimate glomerular filtration rate (GFR) in patients with muscle loss, which is particularly common among patients with cancer. Serum cystatin C may perform better than creatinine in such patients, but its accuracy is affected by obesity. We performed body composition analysis using computed tomography scans in 545 adult patients with cancer and found that both sarcopenia and high adiposity were independently associated with greater discrepancies in serum creatinine-vs. cystatin C-based estimated GFR. These findings highlight the need for future studies to improve and personalize GFR assessment in patients with cancer, particularly in those who will receive renally cleared medications and anti-neoplastic therapies with a narrow therapeutic index.