Statistical analysis

Continuous variables were presented as mean ± standard deviation (SD), and the independent samples t-test was employed to compare intergroup differences between the Total Intravenous Anesthesia-Propofol (TIVA-P) group and the Inhalational Anesthesia-Sevoflurane (IA-S) group. Frequency variables were expressed as n (%) and analyzed using a chi-square test.

Kaplan–Meier survival curves were constructed based on group differences and analyzed using the log-rank test. Univariate and multivariate analyses were performed using the Cox proportional hazards regression model. The hazard ratio (HR) and 95% confidence interval (CI) were used to estimate relative risks. The following covariates were adjusted in the models: age, gender, body mass index (BMI), smoking or alcohol consumption status, histological type, American Society of Anesthesiologists (ASA) stage, type of surgery, tumor location, presence of lymphatic or perineural invasion, and neoadjuvant or adjuvant therapy.

To explore the joint effects of PNI change with propofol-based or sevoflurane-based anesthesia on the prognosis of patients following CRC surgery, we incorporated product terms into the Cox regression models to evaluate the interactions.

The data were analyzed using SPSS 25.0 (SPSS Inc., Armonk, New York) and R 3.6.3 (http://www.r-project.org/). All statistical tests were two-sided, and a significance level of P < 0.05 was applied to determine statistical significance.