Circulating Cell-Free DNA in Plasma of Never Smokers with Advanced Lung Adenocarcinoma Receiving Gefitinib or Standard Chemotherapy as First-Line Therapy

PURPOSE: Circulating cell-free DNA (CFDNA) was investigated as potential screening or prognostic markers in a variety of cancers. This study investigated its clinical significance in a homogeneous group of lung cancer patients. EXPERIMENTAL DESIGN: We analyzed the blood samples of 134 never smokers with advanced lung adenocarcinoma, who were enrolled in a prospective randomized phase III study (First-SIGNAL) comparing gefitinib with gemcitabine plus cisplatin (GP) as first-line therapy. The amount of plasma CFDNA was measured by real-time quantitative PCR targeting the human ACTB genomic sequence. The patients were divided into three groups according to the tertiles of baseline plasma CFDNA. RESULTS: Baseline plasma CFDNA did not correlate with primary tumor size (P = 0.961), whereas the number of metastatic sites correlated significantly with baseline plasma CFDNA (P = 0.015). In the GP arm, the low-CFDNA group showed a lower response rate than the middle- or high-CFDNA group (26.1%, 57.9%, and 60.9%, respectively; P = 0.035). However, in the gefitinib arm, there was no difference in response rate between the three CFDNA groups (57.1%, 47.4%, and 51.9%; respectively; P = 0.825). The high tertile CFDNA group showed a significantly shorter survival than the low tertile CFDNA group (median overall survival, 16.0 vs. 28.6 months, respectively; P = 0.030). The risk of death increased with increased baseline plasma CFDNA (HR = 1.23, 95% CI, 1.01-1.50; P = 0.045). CONCLUSION: High plasma CFDNA is associated with aggressive tumor behavior and poor survival outcomes in these patients.