Abstract
Background & objectives: SHOX2 DNA methylation (mSHOX2) has been shown previously to identify lung cancer in bronchial aspirates and a test for mSHOX2 is available in Europe as an IVD test to aid pathologists in the diagnosis of lung cancer. DNA methylation biomarkers can also be used to detect tumor-derived circulating DNA in blood. The objective of the present study was to develop a modified assay for detection of mSHOX2 in plasma and to evaluate the clinical performance in patients.
Methods: A real time PCR duplex assay originally developed for quantification of mSHOX2 in a high background of unmethylated DNA in bronchial aspirates was modified for the unique requirements of plasma. Following assay optimization, quantitative real-time PCR was used to analyze mSHOX2 in plasma samples (n = 411). A training study was performed to determine a cut-off for patient classification (n = 20 lung cancer patients, n = 20 controls) and the resulting cut-off was verified in a testing study (n = 202 stages I – IV lung cancer patients, n = 169 controls, including patients with other cancers like e.g. of prostate).
Results: The assay reliably detected 15 pg of methylated DNA in a background of 50,000 pg unmethylated DNA. The mSHOX2 assay differentiated lung cancer patients from controls with a sensitivity of 60% and a specificity of 90%. Patients with stages II (72%), III (55%) and IV (83%) lung cancer were detected at a higher sensitivity as compared with stage I patients (27%). Small-cell lung cancer (80%) and squamous cell carcinoma (63%) were detected at higher sensitivity than adenocarcinoma (39%).
Conclusions: mSHOX2 is a promising biomarker for detection of malignant lung disease in plasma.
- © 2011 ERS
