Cytokeratin 20 improves the detection of circulating tumor cells in patients with colorectal cancer

• CK20 is a biomarker for circulating tumor cells (CTC) in colorectal cancer patients.
• CTCs were detected in 89% of the patients using CK20 as additional biomarker.
• CK20 improves the detection rate of CTCs in colorectal cancer patients.

Cytokeratin 20 (CK20) is a well-established marker for colon epithelium. Herein, we suggest that CK20 is a biomarker for detecting circulating tumor cells (CTCs) in patients with metastatic colorectal cancer. Blood specimens (7.5 mL) were collected during surgery after liver mobilization from 25 patients with colorectal cancer. The FDA approved CellSearch™ system and two panels of antibodies against cytokeratins, cytokeratin 8, 18 and 19 (CK8/18/19) and CK8/18/19/20, were used for the detection of CTCs. All the patients' samples were processed using the anti-CK8/18/19 panel. The number of detected CTCs was low, 52% of the patients lacked CTCs and 40% had ≤ 2 CTCs/7.5 mL blood. Nine of the patients' blood samples were processed with both antibody panels. The detection rate of CTCs was significantly higher using the anti-CK8/18/19/20 panel compared with the anti-CK8/18/19 panel, p-value 0.0078. Our data show that inclusion of CK20 as a biomarker efficiently improves the detection of CTCs in colorectal cancer patients. The finding in our study is of clinical importance since a new prognostic biomarker would provide an important tool in individual clinical decision-making for colorectal cancer patients.