Fluctuation of circulating tumor cells in patients with lung cancer by real-time fluorescent quantitative-PCR approach before and after radiotherapy

Background and Aims: The failure to reduce the mortality of patients with solid tumours is mainly a result of the early dissemination of cancer cells to secondary site, which is usually missed by conventional diagnostic procedures used for tumour staging. The possibility to use easily accessible body fluids as a source for circulating tumour cells (CTCs) detection enables longitudinal observations of the disease. In the study, we evaluated the CTCs in lung cancer following locoregional radiation therapy.
Methods: Samples of 5ml peripheral blood was taken from each lung cancer patients (n=15) both before and after the radiotherapy course. Meanwhile tumour size was determined by chest X-ray or computed tomography. Using cytokeratin 19(CK19) as marker,the blood samples were subjected to real time RT-PCR assay. All patients with lung cancer were treated with primary definitive and mediastinal radiotherapy. Results Compare to that of pre-treatment, the value of CK19 mRNA in peripheral blood after therapy decreased dramatically(5.0932±1.0628 vs. 4.2493±0.8323,t=3.192,P=0.007). The change of CK19 mRNA level before and after radiotherapy was closely related to the type (NSCLC vs. SCLC, 0.5389±0.9030 vs. 1.6826±0.9467,t=2.1465,P=0.051). Meanwhile, there appeared to be a close link between the grade (Well/Mod vs. Poor) and the change of CK19 mRNA (0.5024 vs. 1.5271,t=2.017,P=0.065). The change of CK19 mRNA level was related to variation of tumour burden during radiotherapy(r=0.0575,P=0.025). Of the 15 cases studied, 12 cases were positive before radiotherapy (12/15,80%). The positive rate was 53%(8/15) after radiotherapy, meaning that four patients converted into negative after radiotherapy.
Conclusions: The disseminated circulating cancer cells can be affected by radiotherapy; meanwhile further more systemic adjuvant treatment should be conducted. Due to concordance between molecular response and radiological remission, assessment of the therapeutic response might be possible by serial quantitative of CTCs.

Keywords
Lung neoplasm, Blood, Polymerase chain reaction, Cytokeratin, Messenger RNA, Radiotherapy