A Case-control Study Supporting the Use of Liquid Biopsy in the Targeted Therapy for Lung Cancer

Backgrounds: Targeted therapy for lung cancer depends on the genetic testing. Liquid biopsy provides a valuablesource for the genetic testing. However, direct evidence was lacking for whether liquid biopsy could guide the targetedtherapy. Methods: In this retrospective study, the admitted patients from Jan 2015 to Feb 2016 were screened througha pre-established database. Patients with metastatic, pathologically-confirmed, and treatment naive non-small celllung cancer who were prescribed with epithelial growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) fromthe guidance of liquid biopsy were enrolled (Liquid group). The mutation status in tumors was not mandatory. Duringthe same period, patients medicated with TKI based on tumor samples were included in the Control group. They wereenrolled in an age-, gender-, performance-, smoking-, and histology-matched manner. Results: We screened 536 patientsand enrolled 26 patients in the Liquid group. Another 26 patients were enrolled in a 1:1 ratio in the Control group.In the Liquid group, a high consistence (84.6%) in EGFR mutation status between liquid and tumor was observed.The best response was partial response in 19 patients (73.1 %), and followed by stable disease in 6 patients (23.1 %).The median progression-free survival was 10.0 months (95%CI: 4.2-15.8 months). In the Control group, a similar diseasecontrol rate (88.4%, P=0.603) and comparable PFS (8.6 months, 95% CI: 7.6-10.4 months, P=0.714, HR=0.657, 95%CI: 0.309-1.396) was found. In the Liquid group, 3 of 4 patients with discordant results between tumor and liquid biopsyshowed treatment responses favoring the liquid biopsy. Conclusion: This study provided direct evidence supportingthe liquid biopsy for guiding the targeted therapy for lung cancer.