Immunomagnetic Separation for Enrichment and Sensitive Detection of Disseminated Tumour Cells in Patients with Head and Neck SCC.

Screening for malignant cells in the blood and bone marrow was introduced as a strategy for the improved detection of tumour spread and may predict the development of distant metastases. The sensitivity of these approaches depends on several factors, including the choice of antibody for immunocytochemistry (ICC) and the number of cells examined. In this study criteria have been defined for scoring cells reactive with a pan-cytokeratin antibody as tumour, by comparing immunostained cells in clinical samples obtained from head and neck cancer patients and a control group without epithelial malignancy. When leucocyte subfractions are prepared by density gradient separation (DGS) from central venous blood obtained from patients with advanced head and neck squamous cell carcinoma (SCC) and screened by ICC, epithelial tumour cells sediment preferentially with the mononuclear cells but may also be detected in the granulocyte (GC) fraction. Some cases were found to have more tumour cells in the GC fraction. Similar results were seen in model experiments. To increase the sensitivity of the ICC approach, the efficiency of positive immunomagnetic selection (IMS) using Dynabeads coated with an antibody recognizing the Ber-EP4 epitope has been compared with negative IMS using anti-CD45 Dynabeads. Tumour cells were recovered from bone marrow aspirates for 2/17 cases using the positive enrichment technique and for 11/17 patients following negative IMS. These findings justify prospective studies incorporating negative IMS to establish the prognostic significance of these disseminated tumour cells for this group of patients.