Clinical Potential of Circulating Tumor Cells in Colorectal Cancer: A Prospective Study

Abstract

Objectives: Circulating tumor cells (CTCs) in the blood have been used as diagnostic markers in patients with colorectal cancer (CRC). In this study, we evaluated a CTC detection system based on cell size to assess CTCs and their potential as early diagnostic and prognostic biomarkers for CRC.

Methods: From 2014 to 2015, 88 patients with newly diagnosed CRC, who were scheduled for surgery, and 31 healthy volunteers were enrolled and followed up in Pusan National University Hospital. CTCs were enriched using a centrifugal microfluidic system with a new fluid-assisted separation technique (FAST) and detected by cytomorphological evaluation using fluorescence microscopy.

Results: Two or more CTCs were detected using FAST in 74 patients and 3 healthy volunteers. The number of CTCs in the CRC group was significantly higher than that in the healthy volunteers (P < 0.001). When a receiver operating characteristic curve was created to differentiate patients with CRC from healthy volunteers, the sensitivity and specificity were almost optimized when the critical CTC value was 5/7.5 mL of blood. When this value was used, the sensitivity and specificity in differentiating patients with CRC from the healthy controls were 75% and 100%, respectively. In patients with CRC with ≥5 CTCs, vascular invasion was frequently identified (P = 0.035). All patients with stage IV were positive for CTCs. Patients with ≥5 CTCs showed a trend toward poor overall and progression-free survival.

Discussion: Our study demonstrated promising results with the use of FAST-based CTC detection for the early diagnosis and prognosis of CRC.

Figure 1.

Representative immunofluorescent images of CTCs in patients with CRC. CTCs were defined as captured cells that were CK+ or EpCAM+, CD45−, and DAPI+ and had a diameter of >8 μm. CK, cytokeratin; CRC, colorectal cancer; CTC, circulating tumor cell; DAPI, 4,6-diamidino-2-phenylindole; EpCAM, epithelial cell adhesion molecule.

Figure 2.

Differentiating patients with CRC from healthy controls using a ROC curve. To identify the optimal CTC threshold value for differentiating patients with CRC from healthy controls, the sensitivity and specificity were optimized using a threshold count of 5 CTCs per 7.5 mL of blood. Red line, reference line; Blue line, ROC curve; CTC, circulating tumor cell; AUC, area under the curve; CRC, colorectal cancer; ROC, receiver operating characteristic.

Figure 3.

Scatter plot of CTC values of healthy controls and patients with CRC. CRC, colorectal cancer; CTCs, circulating tumor cells.

Figure 4.

Kaplan–Meier survival plots of CTC-positive vs -negative patients. (a) Overall survival. (b) Progression-free survival. CTC, circulating tumor cell.