Lung cancer accounts for 30% of all deaths from cancer. Detection often occurs at an advanced stage and conventional chemotherapy is of limited effectiveness.There is no validated screening approach for early detection of lung cancer. Spiral computed tomography and fluorescence bronchoscopy are being examined, but both might lack diagnostic sensitivity and specificity.Epigenetic-mediated gene silencing in the form of aberrant promoter hypermethylation constitutes an alternative to coding-region mutation for loss of gene function.Loss of gene transcription by promoter methylation is a crucial event in lung cancer initiation and progression. Genes involved in all aspects of normal cellular function are silenced by methylation.The development of the methylation-specific PCR assay enabled the rapid identification of genes that are methylated in cancer. The high sensitivity and specificity of this assay also makes it feasible to detect gene methylation in biological fluids where heterogeneity exists between normal and premalignant/cancer cells. The detection of gene-specific promoter methylation in sputum in people who developed squamous-cell lung cancer provided the first proof of concept that methylation changes could potentially be used as a molecular marker system in screening for early lung cancer.

Silencing of genes by aberrant promoter hypermethylation is now recognized as a crucial component in cancer initiation and progression. Highly sensitive assays have been developed to assess gene-promoter methylation in biological fluids. The detection of methylated genes in sputum could lead to the development of a screening test to non-invasively identify early cancer in high-risk people.