Impact of the serum creatinine and cystatin C ratio for prediction of sarcopenia and prognosis in biliary tract cancer

Abstract

Background Sarcopenia is a poor prognostic factor in cancer patients. In recent years, there have been reports that serum creatinine and cystatin C (Cr/CysC) ratio is associated with sarcopenia. However, the prognostic value of the Cr/CysC ratio in biliary tract cancer is unclear. We evaluated the impact of the Cr/CysC ratio on sarcopenia and prognosis in biliary tract cancer. Methods We retrospectively reviewed the records of 190 patients with biliary tract cancer who had undergone surgical resection from January 2017 to March 2023. Frozen serum samples collected at the time of surgery were used to measure CysC. We calculated the Cr/CysC ratio and investigated the relationship with sarcopenia and the prognostic significance. Results Serum Cr/CysC ratio was statistically related to both skeletal muscle index and handgrip strength, both of which are diagnostic criteria for sarcopenia (skeletal muscle index: R² = 0.096, p < 0.001, handgrip strength: R² = 0.20, p < 0.001). The optimal cutoff value of the Cr/CysC ratio for sarcopenia was 0.848. The low Cr/CysC ratio group was significantly associated with higher preoperative CRP and lower albumin, lower skeletal muscle index, lower handgrip strength, and higher intramuscular adipose tissue content. In multivariate analysis, patients with a low Cr/CysC ratio showed poorer overall survival (hazard ratio 2.60, 95% confidence interval 1.07–6.29, p = 0.033), which was significantly worse than in those with a high Cr/CysC ratio. Conclusions The Cr/CysC ratio could be used as a marker to evaluate sarcopenia in patients with biliary tract cancer. Moreover, a low Cr/CysC ratio predicts poor prognosis in biliary tract cancer patients.