Measurements of total DNA and methylated tumor suppressor genes in the plasma of patients with metastatic non-small cell lung cancer (NSCLC) before, and after chemotherapy, as potential biomarkers for response to treatment

7203 Background: Measuring DNA in plasma using quantitative RT-PCR is a promising method for the detection and surveillance of NSCLC. Detection of methylated genes may be more specific than total DNA for the presence of cancer. Methods: We undertook a prospective trial measuring total DNA, and the levels of 5 commonly methylated tumor suppressor genes in the plasma of a planned 200 patients with metastatic NSCLC before, and up to 3 times during chemotherapy. Blood samples are coincident with radiologic response assessments by RECIST. Blood is collected in Na citrate, gel density gradient tubes spun at 1800 RCF for 20 min, plasma removed without disturbing the mononuclear layer, and frozen at -80°C. DNA is extracted from a fixed volume of plasma, and measured using quantitative PCR of the β-Actin gene. DNA is treated with sodium metabisulfite solution which converts unmethylated cytosines to uracil. For methylation-specific RT-PCR, primers and probes have been designed to amplify bisulfite-converted DNA in...