An Ex vivo cultivation model for circulating tumor cells: The success rate and correlations with cancer response to therapy

BACKGROUND: Cancer mortality is closely linked to recurrence and distant metastasis, posing challenges in real-time tracking due to the invasiveness of current methods. Circulating tumor cells (CTCs) show promise as potential tools; however, their scarcity remains a significant obstacle.

METHOD: In this prospective study, we validated a simple culture protocol and investigated the correlation between clinical response and CTC growth status. Following negative selection, the isolated cells were subjected to ex vivo cultivation in a two-dimensional environment supplemented with cytokines for up to 21 days, followed by immunofluorescence staining for analysis.

RESULTS: Among 37 participants with solid tumors and distant metastasis (34.8% head and neck cancer), 47 samples were collected, from which CTCs were detected. The percentages of CTCs, atypical CTCs, and white blood cells during cultivation from days 7-21 were significantly different (p < 0.001, p < 0.001, and p = 0.330, respectively). Patients were further categorized into progressive disease (PD) and non-PD groups based on disease status, revealing significant differences in CTC growth rates, which increases from Days 7-21 between groups (5.5x vs. 2.8x growth, respectively; p < 0.001).

CONCLUSION: With the proposed protocols, we cultured CTCs from patients with various cancers for 21 days and identified a tool for predicting cancer response. The actual cancer status (PD or non-PD) at CTC isolation correlates to CTC growth rate, guiding the required observation time and parameters for culture.