Detection of circulating tumor cells (CTCs) in patients with lung carcinoma by real-time fluorescent quantitative-PCR approach before and after chemotherapy

Circulating tumour cells (CTCs) are referred to the tumour cells that disseminated from the primary tumour and survive in circulating during the proceeding of tumour growth. As surgical treatment evolves and local control has improved, the failure of cancer treatment has largely remained the result of systemic metastasis. Selection of patients most likely to benefit from adjuvant strategies remains problematic. In order to develop a new standard of curative effect, this study was designed to track the number of CTCs in patients with lung cancer during chemotherapy. Methods: Samples of peripheral blood was taken from each lung cancer patients (n=32) on the day before chemotherapy as well as the third week after the chemotherapy cycle. The samples were subjected to real-time fluorescent quantitative reverse-transcriptase polymerase chain reaction (fqRT-PCR). Meanwhile the tumour size was determined by chest X-ray or computed tomograghy. Results Compared to that of pre-chemotherapy, the expression level of cytokeratin (CK) 19 in the patients significantly declined after chemotherapy (t=4.659,P=0.000). The level of CK19 mRNA in patients with small cell lung cancer (SCLC) was higher than that of patients with non-small cell lung cancer (NSCLC) (t=1.944, P=0.061). The decrease of CK19 mRNA level correlated well with the type during the treatment. Relatively the decrease of SCLC is more obvious (t=6.073,P=0.000). The variation of CK19 mRNA level before and after chemotherapy was positively related to the disparity of tumour burden (r=0.593). There was also a significant association between the type (NSCLC vs. SCLC) and the change of tumour size (t=3.686, P=0.001).The positive rate before chemotherapy was 71.9% (23/32), while that after chemotherapy was 37.5% (12/32), indicating that 11 patients converted into negative after chemotherapy. Of the 16 patients which were in IV-stage, 11 cases were positive (11/16,68.8%). Surprisingly, of the remaining 16 patients which were II/III stage, 12 cases were regarded as positive according to the criteria (12/6,75%). Conclusions: The real-time fluorescent quantitative-PCR approach is useful for measuring the relative number of CTCs in a patients’ peripheral blood to monitor the effectiveness of treatment, and for designing more comprehensive and reasonable therapeutic regimes at earlier dates for patients. The treatment response can be immediately assessed by serial quantitation of CTCs after chemotherapy, and therefore this method highlights an alternative approach to rapidly access the patient’s response to treatment.