Detecting circulating tumor cells in metastatic breast cancer patients using fiber-optic array scanning technology

Abstract

1022 Background: Circulating tumor cell (CTC) detection and enumeration has been shown to be a valuable tool for determining prognosis in metastatic breast cancer patients. CTCs are rare, existing in the circulation at estimated concentrations of 1 in 1 - 10 million normal blood cells. To date, the most widely used technique to detect CTCs has used immunomagnetic enrichment based protocols. In this validation study, we sought to determine if an enrichment free approach using an immunofluorescent cell attachment protocol along with fiber-optic array scanning technology (FAST) could achieve similar results. Methods: We have developed and validated a scanning instrument using FAST that can be used in conjunction with an immunofluorescence staining protocol to efficiently detect CTCs. The protocol uses a pan anti-cytokeratin antibody cocktail directed against 9 cytokeratins along with a DAPI nuclear counterstain. FAST defines cell positions, so relocation and retrospective analysis of CTCs is possible. Using this system, we assayed 50 blood specimens obtained from metastatic breast cancer patients. Pathologic review of CTCs was performed identifying CTCs as cytokeratin positive and DAPI positive. Survival analyses were determined using Kaplan-Meier analyses. Results: 31 women with metastatic breast cancer were enrolled in the study and provided 50 peripheral blood specimens. The median CTC count for patients with progressive disease was 8.5, while the median CTC count for patients with stable or responding disease was 1. At a median follow-up of 1 year, 11 patients had died. Patients with =5 CTCs had a median survival of 212 days, while the median survival for patients with 0–4 CTCs had not been reached after 1 year (p=0.0012). Patients with progressive disease had significantly higher CTC counts (p<0.0001) than those who were stable or responding to therapy. Conclusions: This study confirms the previously reported efficacy of CTC enumeration in determining the prognosis of metastatic breast cancer patients and establishes the potential utility of the FAST cytometer as a method for CTC enumeration. No significant financial relationships to disclose.