110P - The correlation between multi-dimensional characteristics of circulating tumor cells (CTC) and treatment response in patients with initially unresectable metastatic colorectal cancer

Background

Conversion therapy is an important treatment for patients with initial unresectable metastatic colorectal cancer(mCRC) to achieve radical resection. Circulating tumor cells (CTC) are one of the important liquid biopsy methods. There is no study to explore their clinical value in predicting the efficacy. The aim of this study is to explore the value of the number and morphology of CTC in predicting the efficacy of conversion therapy in initial unresectable mCRC patients.

Methods

This study prospectively collected eligible patients with initially unresectable mCRC who were initially diagnosed in Zhongshan Hospital from November 2020 to June 2021. At baseline, after treatment, and before and after conversion resection, multi-point blood sampling was performed. CTC detection using ChimeraX ® Platform; Morphological typing is based on the CTC morphological data of 2083 patients with colorectal cancer who underwent CTC detection in Zhongshan Hospital. Cell Profiler is used for cell feature assignment, clustering and typing.

Results

A total of 126 eligible patients with mCRC participated in this study. According to morphology, CTC can be divided into four morphological types: T1-T4. All 126 patients underwent baseline CTC testing, and 103 patients underwent CTC testing after conversion therapy. After conversion therapy, the positive rate and detection number of CTC significantly decreased (85.7% vs 60.2%, 1.71 vs 1.15, P=0.0052); The detection number of T3 and T4 subtypes significantly decreased (T3: 0.87 vs 0.52, P=0.0026, T4: 0.25 vs 0.06, P<0.0001). The objective response rate was significantly correlated with the baseline number of CTCs (69.8% vs 50.8%, P=0.029), but not significantly with the number of CTCs after treatment. The objective response rate of patients with T3T4 dominance was significantly higher than that of patients with T1T2 dominance (67.6% vs 47.1%, P=0.042). The number of CTC was correlated with patient progression free survival, and baseline CTC positive patients had a worse prognosis (P=0.0012).

Conclusions

The number and morphology of CTCs have good therapeutic and prognostic value for patients with initial unresectable mCRC.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.