To investigate the ability of preoperative urea-creatinine ratio (UCR) to predict long-term postoperative prognosis and to validate the relationship between UCR and muscle mass in patients with colorectal cancer.

Clinical data of 221 colorectal cancer patients from January 2015 to January 2019 were retrospectively analyzed. The patients were divided into two groups according to the UCR optimal cut-off value of 2.65 to explore the relationship between UCR and 3-year prognosis of the patients. Kaplan-Meier plotting of survival curves was done and compared by Log-Rank test. Correlation analysis was performed between patients' preoperative UCR and muscle parameters. Independent t test and nonparametric rank-sum test were used for normally and non-normally data, respectively. Categorical variables were tested using the χ² test. P<0.05 was statistically significant.

There were 22 deaths and 29 recurrences within 3 years. Multivariate analysis showed that UCR and tumor stage were significantly associated with postoperative overall survival (OS) and recurrence-free survival (RFS) （P<0.05）. In all patients, the ROC area predicting 3-year overall survival and recurrence was 0.789 （P<0.001） and 0.739 （P<0.001）, respectively; the risk of death and recurrence was more significant in the high UCR group compared with the low UCR group （P<0.007）. In addition, UCR level was significantly associated with skeletal muscle mass （P<0.01）.

UCR levels are effective in predicting the long-term prognosis of colorectal cancer patients after surgery. Patients with a higher UCR have an increased risk of death and tumor recurrence. In addition, UCR is positively correlated with skeletal muscle mass.