Relationship between the creatinine/cystatin C ratio and muscle mass measured by CT-scan in cancer patients

Background: Sarcopenia is observed in about 50% of cancer patients. Cancer-related sarcopenia nega-tively affects survival and is a predictive factor of anticancer drug toxicity. Sarcopenia diagnosis is challenging in routine care. We investigated whether plasma creatinine and cystatin C predict sarcopenia diagnosis in the specific population of cancer patients.Methods: Two common diagnostic criteria of cancer-related sarcopenia based on skeletal muscle mass +/- handgrip strength were separately applied as the "gold standard" sarcopenia definition. Four sarcopenia indexes based on creatinine and cystatin C values were evaluated: Creatinine/Cystatin C, Glomerular Filter rate (GFR) Cockroft-Gault/GFR CKD-EPI, GFR Cockroft-Gault/GFR Grubb and GFR Cockroft-Gault/GFR simple. The receiver operating characteristic (ROC) curves and the area under the ROC curves were applied to evaluate the sarcopenia diagnostic accuracy of the four different sarcopenia indexes.Results: A total of 99 patients were included. Among them, 47.5% were overweight or obese. The ratio creatinine/cystatin C (ratio value at 0.8) more accurately predicts the diagnosis of sarcopenia in the entire population based on low skeletal muscle mass and low handgrip strength (sensitivity, specificity, ac-curacy and Youden index at 0.77, 0.57, 0.90, 0.34 respectively). The other evaluated ratios predict sar-copenia with a lower specificity in all conditions. In the overweight/obese group, the results are similar. The ratio creatinine/cystatin C (ratio value at 1) accurately predicts sarcopenia with a sensitivity, a specificity, an accuracy and a Youden index at 0.50, 0.86, 0.95, 0.36 respectively in overweight/obese population. Conclusions: The creatinine/cystatin C ratio is a useful and simple biomarker to predict sarcopenia in cancer patients. Moreover, this sarcopenia index also seems to be a strong sarcopenia diagnosis biomarker in overweight and obese cancer patients. Our results must be confirmed in a larger cohort.(c) 2022 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.