POU5F1 and cholangiocarcinoma: Moreover, the multivariate Cox regression analysis revealed that OCT4−CTC (versus none CTC) (HR = 3.560, P = 0.037), OCT4+CTC (versus none CTC) (HR = 6.752, P = 0.001), and treatment line of second or above (versus first) (HR = 2.587, P = 0.013) were independently associated with poorer PFS in advanced CCA patients (Fig. 4B).