Background:

The role of circulating tumor cells (CTCs) in metastatic cancers for predicting overall survival has been well established. The effectiveness of three- or six-month adjuvant therapy in colorectal cancer estimation has shown an association between CTCs and the emergence of resistant cell clones. The presence of CTC clusters indicates increased aggressiveness in epithelial cancers. However, the presence of CTC clusters has not been evaluated in large patient populations. Here, we demonstrate the distribution and prognostic significance of CTCs and CTC clusters in epithelial cancer patients.

Methods:

Retrospectively, blood samples from 3458 patients were analyzed for the presence and distribution of CTCs and CTC clusters using the DCGI-approved OncoDiscover platform, which uses an immunomagnetic multicomponent system mediated by an anti-EpCAM antibody. A total of 1.5 mL of peripheral blood was analyzed to capture cells and clusters from head and neck, breast, and lung cancer patients. The sensitivity, specificity, and accuracy of the OncoDiscover assay had been previously established. CTCs and clusters were identified using CK18 positive, DAPI positive, and CD45 negative staining with automated motorized fluorescence microscopy. CTC clusters were defined as the presence of two or more CTCs bound together.

Results:

Out of 3458 epithelial cancer patients, 65.52% (2262 patients) showed the presence of CTCs, with CTC numbers varying from 1–9 per 1.5 mL of blood. Meanwhile, 7.54% of patients showed CTC clusters, corresponding to 261 clusters. The total number of captured CTCs and clusters was 19,345, with a mean distribution of 5.59. Among these, CTCs accounted for 19,037 (98.41%), while clusters accounted for 308 (1.59%). The highest number of CTCs was observed in head and neck cancers (52.98%) and breast cancers (22.75%), followed by lung cancer (5.65%). In contrast, clusters were most frequently observed in breast cancers (26.95%), followed by lung cancer (16.23%).

Conclusions:

The frequency and distribution of CTCs and CTC clusters were evaluated in epithelial cancers. Patients with CTCs alone and those with both CTCs and CTC clusters represent a more aggressive disease state and a higher likelihood of disease progression. The effectiveness of adjuvant therapy in epithelial cancers may be estimated using CTC and cluster analysis, as their presence may indicate treatment resistance and the emergence of resistant cell clones.