Creatinine–cystatin C ratio and mortality in cancer patients: a retrospective cohort study

Background: Muscle wasting is prevalent in cancer patients, and early recognition of this phenomenon is important for risk stratification. Recent studies have suggested that the creatinine–cystatin C ratio may correlate with muscle mass in several patient populations. The association between creatinine–cystatin C ratio and survival was assessed in cancer patients. Methods: A total of 3060 patients who were evaluated for serum creatinine and cystatin C levels at the time of cancer diagnosis were included. The primary outcome was 6-month mortality. The 1-year mortality, and length of intensive care unit (ICU) and hospital stay were also evaluated. Results: The mean age was 61.6 ± 13.5 years, and 1409 patients (46.0%) were female. The median creatinine and cystatin C levels were 0.9 (interquartile range [IQR], 0.6–1.3) mg/dL and 1.0 (IQR, 0.8–1.5) mg/L, respectively, with a creatinine–cystatin C ratio range of 0.12–12.54. In the Cox proportional hazards analysis, an increase in the creatinine–cystatin C ratio was associated with a significant decrease in the 6-month mortality (per 1 creatinine–cystatin C ratio, hazard ratio [HR] 0.35; 95% confidence interval [CI], 0.28–0.44). When stratified into quartiles, the risk of 6-month mortality was significantly lower in the highest quartile (HR 0.30; 95% CI, 0.24–0.37) than in the lowest quartile. Analysis of 1-year mortality outcomes revealed similar findings. These associations were independent of confounding factors. The highest quartile was also associated with shorter lengths of ICU and hospital stay (both P < 0.001). Conclusions: The creatinine–cystatin C ratio at the time of cancer diagnosis significantly associates with survival and hospitalization in cancer patients.