CLCA1 and colorectal carcinoma: In addition, compared to that in patients with early-stage CRC (TNM stage I and II), the CLCA1 serum expression level was significantly reduced in patients with local or distant metastasis (TNM stage III and IV) (1.24 ± 0.86 ng/mL vs 0.88 ± 0.53 ng/mL, P = 0.013, t-test, Fig. 2b).