Clinical Application Of Plasma DNA Quantification In Chemotherapy For Patients With Advanced Lung Cancer

BackgroundLung cancer is worldwide the most common cancer, its morbidity and mortality are in the forefront of all cancers. 70%~80% lung cancer patients were detected in advanced stages due to lack of effective means of early diagnosis. Lesions may have been beyond the scope of resection. Chemotherapy is the treatment usually chosen to prolong the survival time of patients who lost the chance of resection. The response of malignant tumors to chemotherapy varies, even if tumors show similar histopathological origins and clinical staging. The dismal survival could be improved through earlier determine the personalized chemotherapeutic regimen. However, there is no short-term evaluation protocol for predicting the efficacy of the therapy to date except for the chest imaging. Personalized chemotherapy could be hardly realized. Plasma DNA, existing in the bloodstream but out of blood cells, is thought to be released into the blood stream through cell lysis, necrosis, apoptosis and active DNA release. Levels of plasma DNA were found to correlate with tumor burden and declined following chemotherapy. Plasma DNA could be used in personalized chemotherapy for patients with advanced lung cancer as an effective predictive indicator.ObjectiveThe aim of this study was to determine the correlation of plasma DNA levels with chemotherapeutic efficacy and survival in patients with advanced lung cancer by tracking the whole treatment, and discuss whether plasma DNA could be a sensitive indicator in personalized chemotherapy.Methods Forty-two patients with newly diagnosed lung cancer from the Department of Oncology of The First Affiliated Hospital of Nanjing Medical University were enrolled in this study between October 2007 and June 2009. The patients consisted of 31 males and 11 females, with a median age of 67 years (range: 44~81). All were inoperable advanced lung cancer patients. 35 patients were NSCLC (non-small cell lung cancer) patients, 7 SCLC (small cell lung cancer) patients. Each patient received first-line chemotherapy. The main regimens of first-line chemotherapy were the GP (Gemcitabine and Cisplatin) regimen and the DC (Docetaxel and Cisplatin) regimen for patients with NSCLC, and the IP (Irinotecan and Cisplatin) regimen for patients with SCLC. Blood samples (2 mL) were withdrawn from a peripheral vein and placed into EDTA-containing tubes from patients received 4~6 cycles before initiation of the first treatment (1~7 days) and then after medication of every chemotherapeutic cycle (3~5 days), as well as from three additional patients before initiation of the first treatment, 24 h after medication and 3~5 days after the first cycle of chemotherapy, followed by 1 600g centrifugation at room temperature for 10 min. The plasmas were then transferred and followed an additional 16 000g centrifugation step at 4oC for 10 min. Control venous blood samples were obtained from 200 healthy volunteers for an annual health check with a median age of 55 years (range: 30~88 years), 127 males and 73 females. DNA was extracted from cell-free plasmas of patients and controls based on principle of magnetic beads binding, then analyzed for the amounts of DNA by duplex real-time quantitative PCR with internal control. In this study, tumor response was assessed every two cycles of chemotherapy by computed tomography (CT) scanning using the Response Evaluation Criteria in Solid Tumors (RECIST) to evaluate chemotherapeutic efficacy.ResultsIn 42 patients, the median value of plasma DNA quantification before chemotherapy was 67.0(40.5~109.3)ng/ml, significantly higher than healthy controls 22.4(16.3~30.4) ng/ml) (P < 0.001). No significant association was observed in patients between plasma DNA and age, gender or smoking history. Only histological type was related to the concentration of plasma DNA. Patients with squamouscarcinoma had lower plasma DNA levels than others (P = 0.030).After first-line chemotherapy, among 39 patients: no patient achieved completeresponse (CR), 21 patients achieved partial response (PR), 7 patients had stabledisease (SD), 10 patients had progressive disease (PD), 1 patient dropped out. Bycomparison with healthy controls, three groups of patients with different therapeuticefficacy showed significantly higher baseline DNA concentrations (P < 0.001).Plasma DNA concentrations of patients with partial response (PR) after first-linechemotherapy showed a significant decrease compared with baseline DNAconcentrations (Before therapy: 66.4ng/ml; After first-line chemotherapy: 22.1ng/ml)(P < 0.001), and no statistical difference from healthy controls (P = 0.418), whereasthere is no significant change in SD or PD patients. Survival analysis showed astatistically better survival time in patients who had lower levels of plasma DNA afterthe third chemotherapy (P = 0.035).The results of monitoring plasma DNA level during the therapy showed, DNAlevels of patients who had partial response progressively decreased to the normalrange after the third chemotherapy and had a longer survival time, while those ofpatients who had stable or progressive disease remained high or increased; and within24 h after medication the levels of plasma DNA increased rapidly, followed by adecrease in the treatment-free period.ConclusionThe change of plasma DNA levels within 3-5 days after medication of chemotherapy could sensitively reflect the response to therapy. Plasma DNA quantification only required a little blood, and had a higher specificity and sensitivity. Our data showed that Plasma DNA could be used in personalized chemotherapy for patients with advanced lung cancer as an effective short-term predictive indicator.