Independent Correlation Between Ki67 Index and Circulating Tumor Cells in the Diagnosis of Colorectal Cancer

Background: The Ki67 index is a biomarker of proliferation, while the circulating tumor cell (CTC) count acts as a metastasis-related biomarker. In this study, we analyzed the potential value of CTC count and Ki67 index in diagnosis of colorectal cancer (CRC). Materials and Methods: A total of 105 patients with CRC undergoing surgery were included in the study. Isolation and identification of CTCs were performed by negative enrichment and immuno-fluorescence in situ hybridization, respectively. Expression of Ki67 was assessed by immunohistochemistry. Results: Patients with CTC count >= 2 were defined as CTC-positive. Ki67 index >= 50% was regarded as highly proliferative. Overall, 71 cases were CTC-positive, while 82 cases displayed a high Ki67 index. CTC count and Ki67 index had no correlation with tumor size, tumor site, age, gender and TNM stages of the patients. CTC count was correlated with tumor size (p=0.018) and Ki67 index with level of differentiation (p<0.001). However, there was no relationship between CTC count and Ki67 index (p=0.198). Conclusion: Our results suggest that CTCs can act as a potent metastasis-related biomarker for the diagnosis of CRC, independently of the Ki67 index.