LUNG CANCER SCREENING OVERVIEW
Lung cancer is the leading cause of cancer death in both men and women in the United States. The number of people who die from lung cancer each year has risen over the past 25 years. The number of people who die from lung cancer is greater than the number of people who die from breast cancer, prostate cancer, and colorectal cancer combined. Several factors increase the risk of lung cancer, particularly cigarette smoking.
This topic review discusses ways to prevent lung cancer and discusses the benefits and risks of screening for lung cancer. Other topics about lung cancer are available separately. (See "Patient information: Lung cancer risks, symptoms, and diagnosis (Beyond the Basics)" and "Patient information: Non-small cell lung cancer treatment; stage I to III cancer (Beyond the Basics)" and "Patient information: Non-small cell lung cancer treatment; stage IV cancer (Beyond the Basics)" and "Patient information: Small cell lung cancer treatment (Beyond the Basics)".)
PREVENTING LUNG CANCER
Cigarette smoking is responsible for almost 90 percent of cases of lung cancer. Exposure to certain substances, such as asbestos, has also been linked to the development of lung cancer. Exposure to secondhand smoke and other environmental factors such as radon and asbestos also increase the risk of lung cancer.
The best way to avoid getting lung cancer is not to smoke. Some smokers believe that once they have smoked for a long while, it does little good to quit. However, studies have shown that smokers who quit decrease their risk of lung cancer when compared to those who continue to smoke. Smokers who quit for more than 15 years have an 80 to 90 percent reduction in their risk of lung cancer compared to people who continue to smoke. (See "Patient information: Quitting smoking (Beyond the Basics)".)
IS SCREENING WORTHWHILE?
Screening is a way to detect a disease in its earliest stages, before a person becomes ill. To be recommended, it must be clear that screening is useful in identifying patients who have the disease in the early stages, and that this discovery can reduce the number of patients who die from the disease.
Some screening exams have proven to make a clear difference in outcomes. Examples are the Pap smear for detection of cervical cancer in women, and colonoscopy for detection of colon or rectal cancer in people over 50 years old. These exams are now part of routine healthcare in the United States.
LUNG CANCER SCREENING EXAMS
Research studies have been done to determine if screening for lung cancer makes sense. In these studies, smokers (who are at the highest risk) are divided into groups. Some groups have screening tests while others have no screening. The groups are then followed over many years. Data are gathered on how many patients in each group are diagnosed with lung cancer, how the cancer was treated, how long the patients with lung cancer survived after treatment, and how many patients died from the disease (mortality).
Chest x-ray — Although many healthcare providers recommend an annual chest x-ray for patients who smoke, studies to date have not shown a clear benefit. In patients who had more frequent chest x-rays, more lung cancers were found at early stages, the cancers were more frequently removable by surgery, and the patients had longer five-year survival (from time of diagnosis) than patients with less frequent x-rays. However, the same number of advanced cancers were found in each group and the death rates for lung cancer were not different. A concern is that since overall death from lung cancer was not significantly different, these findings may represent overdiagnosis (finding cancer that would not affect health during a person’s lifetime). Chest x-ray is not recommended for lung cancer screening.
Computed tomography (CT scan) — A large randomized trial in the United States compared the benefits of screening by low-dose CT scan or chest x-ray in smokers (at least a 30 pack-year history, including current smokers or people who had quit in the previous 15 years). Compared to chest x-ray, low-dose CT scan reduced the risk of death from lung cancer by 20 percent, and the overall risk of death by about 7 percent. However, nearly a quarter of the patients who had annual CT screening for three years had an abnormal test, and more than 95 percent of the abnormal tests were “false positive” meaning that they did not represent cancer. False positive tests require follow-up tests, such as more x-rays or biopsies, and these follow-up tests carry risks such as increasing radiation exposure, and complications from biopsy procedures. Thus, there are significant downsides to screening. Additionally, screening may be costly and it is unclear whether insurance companies will pay for it.
The results of this trial are encouraging, but it is not certain if the decrease in mortality would also occur with CT screening outside of the research setting. The patients enrolled in the trial were healthier than the average smoker in the United States, and the doctors involved in the trial might be better than other doctors at reading low-dose CT scans and investigating abnormal findings. Patients with increased risk for lung cancer (similar to or greater than the risk of the participants in the trial) should discuss the risks and benefits of low-dose CT screening with their doctors, and recognize that the most important way to prevent lung cancer is to stop smoking. Patients who choose screening should have a yearly scan, and make sure that follow-up of any abnormal finding is done by doctors who are expert in diagnosing lung cancer.
Other large randomized controlled trials of screening with low-dose CT chest screening are underway and the results are anticipated in the next few years.
Sputum tests — Some studies have looked at the efficacy of analyzing a patient's sputum for evidence of cancer cells in order to detect lung cancer. So far, no clear benefit to this approach has been found. Additional studies that use new technologies to examine the sputum are underway.
PET scan — Researchers are looking at a number of other tools in an effort to help identify patients with lung cancer. Positron Emission Tomography (or PET scanning, which uses a small amount of radioactivity to provide a detailed picture of an organ's function) has been used in combination with CT scanning (PET/CT). However it involves a higher dose of radiation than CT alone and benefit has not been shown for screening purposes.
Other studies — Direct visualization of the lungs with bronchoscopy and breath analysis for cancer markers are two tests that may be used in future studies.
- Patients who smoke are at significantly increased risk of developing lung cancer. The best way to avoid lung cancer is not to smoke. Even long-term smokers can benefit from quitting.
- Researchers are looking for ways to help smokers and non-smokers who develop lung cancer live longer. Early detection and screening is a major focus of this effort.
- Screening with yearly low dose CT scan decreased mortality in a randomized trial of patients with increased risk due to smoking. However, many patients had abnormal tests that did not turn out to be lung cancer. Whether or not to be screened should be based on a discussion of risks and benefits with a healthcare provider, and include evaluation of the patient’s risk, the costs involved in screening, and the expertise of the center where the screening would be done.
- Screening with chest x-rays is not recommended.
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Lung cancer screening (The Basics)
Patient information: Cancer screening (The Basics)
Patient information: Non-small cell lung cancer (The Basics)
Patient information: Lung cancer (The Basics)
Patient information: Small cell lung cancer (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Lung cancer risks, symptoms, and diagnosis (Beyond the Basics)
Patient information: Non-small cell lung cancer treatment; stage I to III cancer (Beyond the Basics)
Patient information: Non-small cell lung cancer treatment; stage IV cancer (Beyond the Basics)
Patient information: Small cell lung cancer treatment (Beyond the Basics)
Patient information: Quitting smoking (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Chemoprevention of lung cancer
Cigarette smoking and other risk factors for lung cancer
Overview of smoking cessation management in adults
Screening for lung cancer
Secondhand smoke exposure: Effects in adults
Women and lung cancer
The following organizations also provide reliable health information.
- National Cancer Institute
- The American Society of Clinical Oncology
- The American Cancer Society