Lung cancer is the most common cancer worldwide and the most common cause of cancer-related deaths in US adults. An estimated 221,130 new cases of lung cancer are expected to occur in the United States in 2011, with an estimated 156,940 deaths.1 Tobacco smoking is the primary risk factor for the development of lung cancer and is thought to account for 90% of all lung cancer diagnoses.2 When compared with never-smokers, persons who have quit smoking still have a 20-fold increased risk of developing a primary lung cancer. In the United States, however, 9% of women and 19% of men who develop lung cancer are considered never-smokers or have smoked fewer than 100 cigarettes in their lifetime.3
HISTOLOGICAL SUBTYPES
There are three forms of non-small cell lung cancer (NSCLC). Adenocarcinoma is more common in light or never-smokers and former smokers.4 This subtype is further delineated to include bronchoalveolar carcinomas and adenosquamous carcinoma. Squamous cell carcinoma is typically seen more often in smokers. Large cell carcinomas constitute 5% of lung cancer diagnoses.4 Small cell lung cancer is a distinctly different subtype; it is typically more aggressive than NSCLC and carries a poorer prognosis.
SCREENING: LOW-DOSE CT OR CHEST
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Historically, diagnosis of lung cancer has been based on the patient's symptoms or is arrived at incidentally. Chest radiograph and sputum cytology have been widely studied as screening tools for lung cancer, but they have not been shown to reduce mortality. In August 2011, the results of the National Lung Screening Trial were published in The New England Journal of Medicine.5 Over a 2-year period, this study enrolled more than 50,000 patients considered to be at high risk for lung cancer. The study included people 55 to 74 years of age with at least a 30-pack-year smoking history and former smokers who had quit within the past 15 years. Participants were randomized to receive three annual screenings using either low-dose CT or single-view posteroanterior chest radiography. The results showed a 20% reduction in mortality from lung cancer for those who underwent low-dose CT compared with those who had chest radiography.5 A 6.7% reduction in all-cause mortality with CT screening was attributed to the discovery of other pathologies, such as granulomatous disease, emphysema, and cardiovascular abnormalities.5
This is a landmark study and will likely change the way most health care providers screen for lung cancer. However, frequency of screening after 3 years and cost remain significant issues. No clinical practice guidelines exist for lung cancer screening, but guidelines are being developed by The American Society of Clinical Oncology (ASCO) and the National Comprehensive Cancer Network (NCCN).