Detection of carcinoma cells in the blood of breast cancer patients

Background: Breast cancers shed cancer cells into the blood soon after they become invasive. We developed an assay for removing these circulating cancer cells. In this study, we wanted to determine the percentage of early stage and metastatic patients with circulating breast cancer cells. Methods: Twenty milliliters of blood were drawn from patients with breast cancer. Epithelial cells were removed by immunomagnetic selection and analyzed by flow cytometry, cytomorphology, and immunocystochemistry. Results: Early stage patients averaged 16 epithelial cells per 20 cc blood whereas metastatic patients averaged 122 tumor cells. Cytomorphology and immunostains confirmed that these were cancer cells. Control blood samples had 1.7 squamous epithelial cells per 20 cc blood. Conclusion: This assay can identify and characterize circulating breast cancer cells. Metastatic patients had more circulating cells than early stage patients. This assay could screen high-risk patients, determine the need for and monitor response to adjuvant therapy, and detect early recurrence of breast cancer.