Challenges in lung cancer screening: a review of implemented programs

Lung cancer is the most common cause of cancer-related death in the world, and smoking is the most prevalent risk factor (1). Although the prevalence of smoking has declined over the last few decades, a staggering 37% of adults in the United States are current or former smokers (2). Despite the knowledge of increased risk in this population, at the time of diagnosis, lung cancer is often already in an advanced stage with 5-year survival as low as 15% (3-5). In the early 1970s, the National Cancer Institute sponsored several large scale studies to evaluate the utility of using chest X-ray film and sputum cytology for lung cancer screening (LCS), however, these studies failed to demonstrate any reduction in mortality (6,7). In 2011, the National Lung Screening Trial (NLST), a multicenter randomized controlled trial, established that screening with annual low dose chest computed tomography (LDCT) provided a 20% relative mortality reduction in individuals at high-risk for developing lung cancer (8). In addition, a 6.7% reduction in all-cause mortality was demonstrated by the NSLT, the highest seen across all cancer screening modalities (8,9). The number needed to screen with LDCT to prevent one death from lung cancer is 320 (10). For comparison, the number needed to screen to prevent one death from breast or colon cancer is 1,904 Review Article