Editorial
Copyright ©2011 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Clin Oncol. Aug 10, 2011; 2(8): 303-310
Published online Aug 10, 2011. doi: 10.5306/wjco.v2.i8.303
Expected clinical applications of circulating tumor cells in breast cancer
Youngjin Park, Tomoaki Kitahara, Tasuku Urita, Yutaka Yoshida, Ryoji Kato
Youngjin Park, Tomoaki Kitahara, Tasuku Urita, Yutaka Yoshida, Ryoji Kato, Department of Surgery, Sakura Medical Center, School of Medicine, Faculty of Medicine, Toho University, Sakura, Chiba Prefecture 285-8741, Japan
Author contributions: Park Y designed the concept for this study; Kitahara T, Urita T and Yoshida Y acquired the data; Park Y, Kitahara T, Urita T, Yoshida Y and Kato R analysed and interpreted the data; Park Y drafted the manuscript; Park Y, Kitahara T, Urita T, Yoshida Y and Kato R critically revised the manuscript for important intellectual content; Kato R supervised the study.
Correspondence to: Youngjin Park, MD, PhD, Associate Professor (Breast Surgery), Department of Surgery, Sakura Medical Center, School of Medicine, Faculty of Medicine, Toho University, Sakura, Chiba Prefecture 285-8741, Japan. youngjinpark@sakura.med.toho-u.ac.jp
Telephone: +81-43-4628811 Fax: +81-43-4628820
Received: May 31, 2011
Revised: July 7, 2011
Accepted: July 14, 2011
Published online: August 10, 2011
Abstract

Tumor cell invasion and intravascular filtration lead to the presence of circulating tumor cells (CTCs) in peripheral blood. CTCs have, thus, been counted in patients with cancer to analyze metastatic mechanisms or in the hope of developing clinical applications for diagnosis and therapy; various CTC-related studies have been performed. However, the clinical significance of CTCs remains to be established because of the extremely small number of CTCs in peripheral blood as compared with the number of blood cells. Technical problems (e.g. reproducibility and reliability) in the detection of CTCs also remain to be solved. The use of flow cytometric analysis, which can be performed with tumor-cell markers such as anti-epithelial cell adhesion molecule antibodies and anti-cytokeratin antibodies and non-tumor-cell markers such as anti-CD45 antibodies has enhanced specificity for the detection of tumor cells. The CellSearch System® can detect 1 CTC in 7.5 mL of peripheral blood, with high reproducibility. Its detection rate and accuracy for CTCs have been confirmed. In the United States, clinical trials have used this system to detect CTCs in patients with metastatic breast cancer, metastatic colorectal cancer, and metastatic prostate cancer, and CTCs have been confirmed to be a useful prognostic factor. This system was also suggested to be useful for monitoring treatment response in patients with metastatic breast cancer and was approved by the United States Food and Drug Administration in 2004. Measuring CTC counts can facilitate the early prediction of treatment response and thereby avoid unnecessary therapy. CTCs may also be a useful biomarker for molecular targeted agents, enabling the identification of patients most likely to respond to a given treatment and facilitating treatment selection. However, the widespread use of CTC monitoring as a routine examination requires a further improvement in measurement sensitivity, the establishment of criteria for quantitative and qualitative evaluations, and additional clear-cut evidence supporting the clinical significance of CTCs. We expect that CTCs will be established to be a new diagnostic and therapeutic index for breast cancer.

Keywords: Breast cancer; Circulating tumor cells