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 negatively 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, accuracy and Youden index at 0.77, 0.57, 0.90, 0.34 respectively). The other evaluated ratios predict sarcopenia 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.