The incidence of bone marrow circulating tumour cells in breast cancer patients is directly related to the size of the primary tumour

Introduction: Metastatic spread of tumours is the most important factor affecting cancer mortality rates. There is, as yet, little scientific research supporting the development of overt metastatic disease from subclinical micrometastatic deposits. We conducted a prospective study investigating the incidence of circulating tumour cells in patients with breast carcinoma. Methods: Pre-operatively, each patient underwent bone marrow aspiration from right rib and bilateral iliac crests. The mononuclear cell layer was isolated using the Ficoll-Paque density centrifugation technique. The cells were stained with both a membrane bound epithelial marker (HEA) and an intracellular marker (MNF116) and analysed using Flow Cytometry. IgG1 FITC (DAKO) was used as a control. Results: From July 2001 to May 2003, 60 patients undergoing definitive surgery for breast carcinoma were enrolled. Tumour size ranged from 1 cm to 4.8 cm. Bone marrow aspiration was successful in all patients. Circulating tumour cells were detected in 46 patients. Tumours less that 2.5 cm had an average of 5.9% HEA positive cells while those greater than 2.5 cm had an average of 19.9%. (p < 0.05) Conclusion: We have demonstrated that the size of the primary tumour is directly related to the incidence of circulating tumour cells found in bone marrow. We conclude that this may contribute to the poor prognosis associated with larger tumours in patients with breast carcinoma.