Flow cytometry as the new ‘gold standard’ for detection of free tumour cells in abdominal lavage fluid in gastric cancer patients: A comparative study of molecular and conventional methods

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Abstract

Aim:

The ideal method for detection of free tumour cells in abdominal lavage fluid should be rapid, reliable and widely available. Flow cytometry potentially covers these properties, but there are only a few studies directly comparing flow cytometry for detecting gastric cancer cells to other methods. Therefore, we compared free tumour-cell detection in abdominal lavage fluids using cytology with immunocytochemistry, RT-qPCR and flow cytometry.

Methods:

Peritoneal lavage fluid samples were collected from 10 patients. Detection of free tumour cells was performed using cytological and immunocytochemical analysis, and using RT-qPCR and flow cytometry. Tumour cells were detected according to CEA and CK20 mRNA expression levels using RT-qPCR, and with the epithelial markers EpCAM/CD326 and CEA using flow cytometry.

Results:

The sensitivity and specificity of cytology were 40% and 100%, respectively, while the RT-qPCR had a sensitivity of 80% and specificity of 100%. Flow cytometry showed no false-negative results and only one false-positive result, giving a sensitivity and specificity of 100% and 80%, respectively. The RT-qPCR and flow cytometry could detect free tumour cells in each of the three false-negative cases with cytology. In the samples with detected tumour cells, tumour cell clusters were observed with imaging flow cytometry, providing additional morphological confirmation.

Conclusion:

The combination of quantitative and qualitative data from flow cytometry and the images of tumour cells in borderline cases provide a rapid, reliable and reproducible method for detection of free tumour cells in abdominal lavage fluid, which is necessary for intraoperative selection of patients for intraperitoneal chemotherapy.

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