Relationship of circulating tumor cells to the effectiveness of cytotoxic chemotherapy in patients with metastatic non-small-cell lung cancer.

The aim of this study was to investigate the relationship of the number of circulating tumor cells (CTCs) with the effectiveness of cytotoxic chemotherapy in patients with metastatic non-small-cell lung cancer (NSCLC). We prospectively evaluated CTCs in the peripheral blood of patients with previously untreated metastatic NSCLC. From May 2008 through August 2010, 33 patients (23 men and 10 women; median age, 64 years; range, 46-74 years) were enrolled. All patients received combination chemotherapy with gemcitabine and carboplatin. The CTCs were captured from samples of peripheral blood with a semiautomated system using an antibody against epithelial cell adhesion molecule. Blood samples with one or more CTC per 7.5 ml were defined as positive. Of total 33 patients, 12 (36.4%) had positive CTCs and 5 (15.2%) had five or more CTCs before chemotherapy. There were no differences in response rates to cytotoxic chemotherapy between CTC-positive patients and CTC-negative patients. On the other hand, the rate of progressive disease in cytotoxic chemotherapy was significantly higher in CTC-positive patients (66.7%) than in CTC-negative patients (23.8%, p = 0.02). In conclusion, the number of CTCs could be a useful predictive factor for the effectiveness of cytotoxic chemotherapy in patients with metastatic NSCLC.