Lung cancer screening guidelines: common ground and differences

Lung cancer is the leading cause of cancer related mortality. There are approximately 159,260 lung cancer related deaths projected for 2014 in the USA, which accounts for one third of all cancer deaths (1). Despite significant advances in medical therapy, the overall 5-year survival rate for lung cancer has only increased from 11.4% in 1975 to 16.6% in 2009 as more than half of the cases are diagnosed at a metastatic stage with a 5-year survival of 3.9% (2). Only 15% cases are stage I at the time of diagnosis, which carries a higher 5-year survival rate of 53.5% (1). These rates give a rationale for lung cancer screening in high risk populations. For decades, tobacco control strategy has remained the cornerstone of lung cancer prevention strategies (3). Despite the reduction in the prevalence of smoking among adults from 43% to 18% (4) in 2010, since the release of US Surgeon General’s statement on impact of tobacco in 1964, the incidence of lung cancer has not been reduced proportionally. Smoking cessation does lowers tobacco attributable cancer risk but the risk never matches that of a non-smoker and a significant percentage of newly diagnosed lung cancers occur in former smokers (5). This pattern points to the evolving carcinogenic damage caused by tobacco smoke which continues despite cessation. Hence, combined efforts at smoking cessation and early screening seem prudent to tackle this ever increasing burden of disease. A decade has passed since the first randomized controlled trial (RCT) using low dose computed tomography (LDCT) was conducted by Garg et al. to assess the feasibility of early screening (6). After years of disappointing results from subsequent trials, a promising screening approach finally emerged with the National Lung Cancer Screening Trial (NLST), which is the most expensive trial ever conducted by National Cancer Institute (NCI) and spanned over a period of 9 years from 2002 to 2011. The trial reported a mortality reduction of 20% with LDCT screening as compared to chest X-ray (CXR) screening (7). NLST is the only completed, adequately powered study for lung cancer screening in a well-defined high risk population with concrete results so far. Since the results of NLST trial, data from NELSON (8) and I-ELCAP (9) projects have also come forth with results which further support the rationale behind lung cancer screening. These results formed the basis of the screening recommendations across almost all the major societies. After an comprehensive review of the literature and existing evidence, the U.S. Preventive Services Task Force