Sarcopenia, adiposity and large discordance between cystatin C and creatinine-based estimated glomerular filtration rate in patients with cancer

Purpose Creatinine-based estimated glomerular filtration rate (eGFR(CRE)) may overestimate kidney function in patients with sarcopenia. While Cystatin C-based eGFR (eGFR(CYS)) 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 eGFR(CRE) and eGFR(CYS) in patients with cancer. Methods We conducted a cross-sectional study of consecutive adults with cancer who had an abdominal CT scan performed within 90 days of simultaneous eGFR(CRE) and eGFR(CYS) 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 cm(2)/m(2) for women,<55 cm(2)/m(2) 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 eGFR(CYS) >30% lower than eGFR(CRE). We estimated the odds of eGFR discrepancy using multivariable logistic regression modeling. Results Of 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). Conclusion Discrepancies in eGFR(CRE) and eGFR(CYS) are common in adult patients with cancer, and sarcopenia and high adiposity are both independently associated with large eGFR discrepancies.