Development of a flow cytometric method to determine DNA ploidy of oesophageal cancer cells obtained by forceps biopsy samples during oesophago-gastro-duodenoscopy.

BACKGROUND The DNA content of oesophageal tumour cells is a prognostic factor in untreated patients. To investigate whether DNA ploidy is useful to select patients for neoadjuvant therapy it is of interest to develop a method allowing reliable flow cytometric analysis of the DNA content of tumour cells obtained by forceps biopsy during endoscopy before start of therapy. METHODS Freshly frozen forceps biopsy samples from 30 patients with oesophageal cancer were disaggregated. DNA was stained with propidium iodide and ploidy was determined by flow cytometry. To enhance sensitivity epithelial cells were simultaneously labelled with anti-cytokeratin antibodies. Results were compared with image analysis. To evaluate the sampling error, parallel measurements were done in 10 patients by image analysis on forceps biopsies obtained during endoscopy before surgery and on the resected tumour. RESULTS The sensitivity to detect aneuploidy was lower for standard flow cytometry than for image analysis (13 versus 33%). The overall sensitivities were identical using a double labelling technique with additional cytokeratin-staining of the epithelial cells, but divergent results were obtained in 2 cases, where detection of aneuploidy was either possible with image analysis or with double labelling flow cytometry only. DNA content of samples gained by forceps biopsies and surgically resected tumours was concordant in 8 of 10 cases. In 2 patients, aneuploidy was detected only in the surgically resected tumour but not in the pre-operatively obtained forceps biopsies. CONCLUSIONS A flow cytometric method for routine determination of the DNA ploidy of cells obtained by forceps biopsies from patients with oesophageal cancer was developed and evaluated against image analysis. The technique allows the prediction of DNA content before tumour resection, and might be used for optimising therapy and the patient's quality of live.