The multivariate Cox regression analysis revealed that OCT4−CTC (versus none CTC) (HR = 4.638, P = 0.024), OCT4+CTC (versus none CTC) (HR = 6.674, P = 0.003), age ≥ 65 years (versus < 65 years) (HR = 2.796, P = 0.018) and treatment line of second or above (versus first) (HR = 2.893, P = 0.016) were independently linked with shorter OS in advanced CCA patients (Fig. 5B). This evidence concerns the gene POU5F1 and cholangiocarcinoma.