Colorectal Cancer CTCs Detection Using Two FCM Protocol Approaches

The presence and quantification of circulating tumor cells (CTCs) could minimize the mortality among cancer patients by tailored, personalized, and targeted therapy and could also help in the field of investigation about new therapeutic targets. Identification of CTCs has been performed using molecular techniques and more advanced automated techniques such as CellSearch® and Amnis®. Our aim was to test the possibility of identifying CTCs in colorectal cancer patients using a lower cost and less complex flow cytometry-based method.

Besides the CellSearch® system for CTCs enumeration and Amnis® Imaging Flow Cytometers, which are both commercially available, we tested and developed two FCM protocol approaches after immunomagnetic enrichment for CTCs enumeration in the blood of colorectal cancer patients. The CTCs numbers were assessed at baseline before anesthesia and the curative surgery and day one after the curative surgery. Blood from healthy donors was used as negative control. The research was performed by the Cyflow® Space cytometer (Partec, Münster, Germany).

In the patient group, the enumeration using the direct protocol with a threshold 3 cells/mL, showed a mean of CTCs before surgery of 32, while after surgery it was 20, with sensitivity (SN) of 49.2% and specificity (SP) of 58.3%. On the other hand, using the intracellular protocol with a threshold of 1 cell/mL in patients' group, the mean of CTCs before surgery was 65 and after surgery it was 60, with a sensitivity (SN) of 62.7% and specificity (SP) of 70%. In the intracellular protocol the most significant correlation identified was for the expression of CKs with adenocarcinomas (r = 0.256, p = 0.044), with the existence of lymph node infiltration (r = 0.380, p = 0.008), and with the stage of the disease (r = 0.391, p = 0.003). For the direct protocol, considerable correlation was found with the samples of the right colon (r = 0.369, p = 0.002).

Our findings demonstrate that we established two FCM low cost protocol approaches to detect and enumerate CTCs in colorectal cancer patients. In both FCM protocols (direct and intracellular) we observed a statistically significant increase (p ˂ 0.05) of CTCs number in the patient group. No statistical significance (p ˂ 0.05) of CTCs before and after surgery in patient group in both protocols was observed.