Lung cancer screening refers to cancer screening strategies used to identify early lung cancers before they cause symptoms, at a point where they are more likely to be curable. Lung cancer screening is critically important because of the incidence and prevalence of lung cancer. More than 235,000 new cases of lung cancer are expected in the United States in 2021 with approximately 130,000 deaths expected in 2021. In addition, at the time of diagnosis, 57% of lung cancers are discovered in advanced stages (III and IV), meaning they are more widespread or aggressive cancers. Because there is a substantially higher probability of long-term survival following treatment of localized (60%) versus advanced stage (6%) lung cancer, lung cancer screening aims to diagnose the disease in the localized (stage I) stage.
Results from large randomized studies have recently prompted a large number of professional organizations and governmental agencies in the U.S. to now recommend lung cancer screening in select populations. The 3 main types of lung cancer screening are low-dose, computerized tomographic (LDCT) screening, chest x-rays, and sputum cytology tests. Currently multiple professional organizations, as well as the United States Preventive Services Task Force (USPSTF), the Centers for Medicare and Medicaid Services (CMS) and the European Commission's science advisors concur and endorse low-dose, computerized tomographic screening for individuals at high-risk of lung cancer.
Current guidelines
The 2021 U.S. Preventive Services Task Force guidelines recommends annual screening for lung cancer with low-dose computed tomography in adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years. Screening should be discontinued once a person has not smoked for 15 years or develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery.
The definition of those considered to be at sufficiently high risk to benefit from screening varies according to different guidelines. The National Comprehensive Cancer Network suggests screening for two high risk groups. Group 1 guidelines include 55–77 years of age, 30 or more pack years of smoking and has quit within the past 14 years, and are a current smoker. Group 2 includes those 50 years of age or older, 20 or more pack years of smoking, and other risk factors excluding second-hand smoke. Other risk factors include contact with cancer-causing agents (radon, arsenic, beryllium, cadmium, chromium, nickel, asbestos, coal smoke, soot, silica, diesel fumes), history of cancer, family history of lung cancer, or a history of COPD or pulmonary fibrosis.
In 2022, the European Commission's Scientific Advice Mechanism concluded that "there is a strong scientific basis for introducing lung screening for current and ex-smokers using the latest technologies, such as low-dose CT scanning".
Risks of screening
Low-dose CT screening has been associated with falsely positive test results which may result in unneeded treatment. In a series of studies assessing the frequence of false positive rates, results reported that rates ranged from 8-49%. The false-positive rate declined when more screening rounds were performed. Other concerns include radiation exposure, the cost of testing alone, and the cost if follow up of tests and screenings. False reassurance from false negative findings, over-diagnosis, short term anxiety/distress, and increased rate of incidental findings are other risks. The currently used low dose CT scan results in a radiation exposure of about 2 millisieverts (equal to roughly 20 two view chest x-rays). It has been estimated that radiation exposure from repeated screening studies could induce cancer formation in a small percentage of screened subjects, so this risk should be mitigated by a (relatively) high prevalence of lung cancer in the population being screened.
Attendance
Deprivation can reduce the numbers of people attending lung cancer screening. A UK study showed that making the screening easily accessible increased take-up. Providing mobile screening units parked in supermarket car parks, for example, in the poorer areas of Manchester was an acceptable way of offering lung checks to high-risk groups such as smokers. A simple test measured obstruction to the flow of air in and out of the lungs. A third of the tests showed airflow obstruction, a sign of chronic obstructive pulmonary disease which is a risk factor for lung cancer and other health conditions.