Circulating tumor cell (CTC) as a clinical marker in malignant pleural mesothelioma (MPM).

Abstract

10572 Background: Circulating tumor cell (CTC), a surrogate of distant micro-metastasis, is potentially useful in the diagnosis of malignant tumors, but its clinical significance in malignant pleural mesothelioma (MPM) remains unknown. The “CellSearch” system is a reliable detection system designed for capturing CTCs of epithelial origin with an antibody against epithelial call adhesion molecule (EpCAM), and in our previous examination, expression of EpCAM was positive in around 50% of MPM tissue samples. Following a promising result of our preliminary study showing the diagnostic value of CTC in MPM (Tanaka F. et al ASCO2008), we conducted a prospective study to evaluate the diagnostic capability and the relation to the clinical outcome. Methods: Patients who presented at our institute with suspicion or diagnosis of MPM were eligible in this study. CTCs in 7.5mL of peripheral blood were captured and quantitatively evaluated with the “CellSearch” system without knowledge of clinical characteristics of each case. Results: Among 170 eligible cases, 137 were finally diagnosed as having MPM and 33 as nonmalignant diseases (NM). CTC was positive (CTC-count, one or more) in 38% (52/137) of MPM cases, and was also positive in 9% (3/33) of NM cases. (p=0.024) CTC-count was significantly higher in MPM (range, 0-27) than in NM (range, 0-1; Mann-Whitney's p=0.019), but receiver operating characteristic (ROC) curve analysis failed to show a significant diagnostic performance of the CTC-test in discrimination between MPM and NM with the area under curve (AUC) of 0.599 (95% confidence interval [CI], 0.501-0.696; p=0.079). The sensitivity and specificity of the CTC-test were 28% and 91%, respectively. In MPM patients, CTC positivity (≥P) and CTC-count significantly increased with tumor progression (p=0.037 and p=0.029, respectively). However, CTC-positivity was not correlated with the prognosis (mean survival time [MST], 427days and 446days for CTC-positive and CTC-negative patienst, respectively; p=0.957). Conclusions: CTC can be detected in the peripheral blood in a small subset of MPM patients, but the CTC-test with the current “CellSearch” system provided no significant clinical value.