Lung cancer is the leading cause of cancer death and the second most diagnosed cancer in both men and women in the United States.
INTRODUCTION
The number one cause of lung cancer is cigarette smoking and use of other types of tobacco (such as pipes and cigars). There are other known causes for the disease, including breathing secondhand smoke, being exposed to substances such as asbestos or radon at home or work, and having a family history of lung cancer.

Since lung cancer is relatively asymptomatic in the earliest stages, the disease is typically detected at an advanced stage when curative treatment is no longer feasible. The delay in diagnosis of the disease is greatly responsible for the low survival rates.  Early detection of lung cancer has, therefore, the potential to significantly reduce mortality by increasing the chances of treating and curing the disease.

STATISTICS
Lung cancer represents the deadliest type of cancer in men and women worldwide. Only in the United States, the National Cancer Institute (NCI) estimated that in 2013 there will be over 228,000 new cases of lung cancer and over 159,000 associated deaths (non-small cell and small cell combined). In 2009, more than 205,000 people were diagnosed with lung cancer, and over 158,000 people died from it (CDC data – U.S.A.).

The incidence of lung cancer is slightly higher in men than in women, but men are about twice more likely to die from the disease. Worldwide 1.6 million cases of lung cancer and almost 1.4 million deaths were recorded in 2008.

LUNG CANCER SCREENING
Lung cancer has many attributes that make it appropriate to consider screening for, including high morbidity and mortality and a relatively high prevalence in high-risk populations. Lung cancer mortality and survival are related to the initial stage of diagnosis, suggesting that treating early may be beneficial; therefore, an effective screening program for the early detection and treatment of lung cancer could have a significant impact on its high mortality rate. In fact, more than 75 percent of people with lung cancer have incurable, locally advanced or metastatic disease at the time of diagnosis, and a five-year survival rate of less than 5 percent. It has been estimated that 10% of all smokers, equivalent to over 110 million people, can benefit from screening (Goulart et al. 2012).
In the early 1990s, low-dose computed tomography (LDCT) was introduced as a screening test with hope that improved sensitivity might improve lung cancer screening outcomes, and several observational studies and randomized, controlled trials began to evaluate this modality in NSCLC. As a results of the National Lung Screening Trial (NLST) results published in 2011 (Aberle et al. 2011) several professional organizations have developed screening recommendations for subjects at risk for developing lung cancer (Humphrey et al. 2012).