Lung cancer screening: from imaging to biomarker

Cancer is the leading cause of death worldwide and accounted for 7.6 million deaths in 2008 with primary lung cancer responsible for 1.37 million deaths alone [1]. There are an estimated 226,160 new cases of lung cancer in 2012 in the United States with approximately 160,340 deaths [2]. The lack of sensitive screening tests for early detection of lung cancer plus ineffective treatment for locally advanced and metastatic disease is responsible for the high mortality rate and the dismal overall five year survival rate [3,4]. With the extensive effort for tobacco awareness education, advancements of imaging and combined treatment modalities, the 5-year survival rate of lung cancer has improved marginally from 12% in 1977 to 16% in 2007 [2]. However, if lung cancer is detected at an early stage, complete resection of the tumor may produce a 5-year survival approaching 67% [5]. Therefore early detection of lung cancer by sensitive screening tests could be an important strategy to improve the prognosis of lung cancer.The results of primary lung cancer screening trials using imaging modalities such as chest X-RAYs combined with sputum sampling, CT scans and LDCT will be reviewed. In addition, the role of serum biomarkers and biological modalities, circulating DNA and RNA, exosomal microRNA and circulating tumor cells (CTCs) and thermogram and nanopore sensor technologies will be discussed.The first large prospective trial using chest X-Ray as a screening tool for the early detection of lung cancer was performed in the UK and published in 1968. In that study there were 29723 men aged 40 years or older who had six-monthly chest radiograph screening for three years compared with a control group of 25311 men who received chest radiograph at the beginning and the end of the study. Lung cancer annual mortality rate did not differ statistically in the two groups, with 62 deaths in the screened group and 59 in the control group, but the 5-year survival rate for participants with l