Finding lung cancer early, when it is easiest to treat, can save lives.
Currently, only 16% of lung cancers are diagnosed while the tumor is still localized—that is, in its earliest stages of growth. A major challenge is that most people with lung cancer only have symptoms when they are in later stages of disease. In fact, it does happen sometimes among those who are diagnosed early that their lung cancer was discovered during treatment for an unrelated medical issue.1
Screening for cancer means checking for cancer before there are any symptoms. Examples of commonly used screening tests for cancer are mammograms for breast cancer, colonoscopies for colon cancer, and the Pap test and HPV tests for cervical cancer. There is not yet a comparable reliable and broadly available screening test for lung cancer that can catch the disease early. A type of high-energy radiation that can go through the body and onto film, making pictures of areas inside the chest, which can be used to diagnose disease are not recommended for screening because they often miss early-stage lung cancers and have not resulted in decreased mortality. Likewise for sputum cytology, a test that checks for abnormal cells in mucus and other matter brought up from the lungs by coughing. There is ongoing research toward developing such a reliable and broadly available lung cancer screening test that can be used for all.2
What is available now, and has proven to be effective for lung cancer screening among high-risk individuals, is a A newer form of CT scan that uses less radiation than a standard chest CT and takes less than one minute to complete (LDCT), which is much more sensitive than chest X-rays. LDCT is recommended for early-detection screening, but only in these high-risk individuals. The usefulness of LDCT in high-risk individuals was confirmed by the National Lung Screen Trial (NLST).
The National Lung Screening Trial (NLST)
The National Lung Screening Trial (NLST) was funded by the National Institutes of Health (NIH). It looked at using a A newer form of CT scan that uses less radiation than a standard chest CT and takes less than one minute to complete (also called low-dose spiral CT or helical CT scan) to screen for lung cancer. Over 53,000 current and former heavy smokers aged 55 to 74 participated at 33 sites across the United States. Starting in August 2002, subjects remained in the trial for a 20-month period and were randomly assigned to receive three annual screens with either a low-dose CT scan or a standard chest X-ray.
The study found that people who were screened with a low-dose CT scan had a 20% lower chance of dying of lung cancer than those who were screened with a chest X-ray.3
Who should be screened for lung cancer?
There are several sets of guidelines, including the ones outlined below, to help determine who should be screened by LDCT for lung cancer. These guidelines have been established in large part from the results of the A National Institutes of Health-funded clinical trial that found using a low-dose CT scan to screen for lung cancer can reduce mortality due to lung cancer. They are very similar, with the differences primarily related to the role of screening for the oldest patients and risk factors other than smoking. All of the patients who are recommended for screening are considered to be at high risk for developing lung cancer but do not currently have any symptoms to suggest that they do have lung cancer. Patients should discuss these guidelines with their doctor and understand the risks and benefits before undergoing LDCT screening.
The guidelines from the US Preventive Services Task Force (USPSTF) include annual screening with LDCT in adults who:
- Are aged 55 to 80 years and
- Have a 30 pack-year smoking history* and
- Currently smoke or have quit within the past 15 years4
*A pack year is the equivalent of one pack (20 cigarettes) smoked daily for one year. To have a 30-pack-year smoking history, a person could have smoked one pack daily for 30 years, two packs daily for 15 years, or any other combination of daily packs x number of years that totals 30.5
The US Preventive Services Task Force recommends that lung cancer screening stop once a person:
- Reaches 81 years of age or
- Has not smoked in 15 years or
- Develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery4
The guidelines from the National Comprehensive Cancer Network (NCCN) include annual screening with LDCT for individuals in two high-risk groups. These are adults who are either:
- aged 55-77 years and
- have smoked for 30 or more pack years and
- is a current smoker or quit smoking within the past 14 years
- aged 50 years and over and
- have smoked for 20 or more pack years and
- have risk factors other than second-hand smoke5
The NCCN guidelines suggest follow-up screening. Usually the next LDCT will occur after one year, but this depends on the doctor's recommendation based on the screening test results.5
The guidelines from the American College of Chest Physicians (CHEST®) include annual screening with low-dose CT scans in adults who are:
- aged 55-77 years and
- have smoked 30 pack years or more and
- either continue to smoke or have quit within the past 15 years6
How is screening done?
Currently, LDCT is used to screen for lung cancer. The scan is a computerized X-ray imaging procedure that yields detailed pictures, or scans, of areas inside the body. Because the scanning produces multiple images from different angles, it can show both two-dimensional and three-dimensional images of anything abnormal in the chest. CT images show more detail than a traditional X-ray.7,8
For lung cancer screening, the CT procedure usually takes only several minutes. During the procedure, the person lies very still on a table. Depending on the scanner, either the table passes slowly through the center of the scanner or the table stays still while the scanner moves around the person. There might be whirring sounds during the procedure. At times during the procedure, the technician operating the equipment will ask the person to hold his or her breath; this prevents blurring of the images.7
A CT scan can provide very detailed information, including the size, shape, or location of an abnormality. However, a scan cannot diagnose whether or not an abnormality is cancer. The doctor may recommend another scan to check for growth of the abnormality or may recommend a biopsy.7
What else should you know about screening?
Despite the benefits of LDCT lung cancer screening, including, among others, decreased mortality from lung cancer, decreased mortality from lung cancer treatment, and improved quality of life, there are some drawbacks and risks, including that LDCT may:
- Find abnormalities that look like small lung nodules that have to be checked with either another scan or a The removal of cells or tissues for examination by a pathologist if considered suspicious. The vast majority of the time these end up not being cancer.
- Miss very small cancers or cancers that are hidden behind other structures in the chest.
- Expose a person to a small amount of radiation. While it is a smaller dose than that from a standard CT scan, it often leads to further CT scans, which in turn results in greater radiation exposure. High doses of radiation exposure can lead to other types of cancer in the future.
- Detect small tumors that would not become problematic
- Have costs for the patient that are not covered by the patient's insurance
- Cause stress while waiting for test results4,7,9,10
Following are some of the factors that should be considered when a person discusses screening with his or her doctor:
- Screening with low-dose CT scans will not find every lung tumor
- Not all tumors that are found will be at an early stage
- A low-dose CT scan may find something that does not end up being cancer
- Screening can only be done at facilities that have the specific type of CT scan, so a person may have to travel to obtain screening
- Screening should be done at a facility that has a multidisciplinary group of experts for screening and for the management of lung nodules or other findings
- Not all insurance plans currently cover CT scan screening for lung cancer. There may be extra costs even if CT scan screening is covered
- For smokers, this is a good time to reconsider smoking cessation efforts and counseling
Choosing a screening center
Ideally, the decision to be screened or not should be made with the help of a person's primary care doctor or pulmonologist. The doctor knows the patient's history and possible risk factors best and can help guide him or her to the right screening center. Some screening centers require a doctor’s prescription in advance for a scan. Others will do an evaluation, also called a risk assessment, without a prescription to determine whether a person's history and risk factors warrant a scan.
The National Comprehensive Cancer Network recommends going to screening centers that:5
- Follow an organized plan that is updated to include new technology and knowledge
- Have a high-quality screening program with enough staff and resources
- Are accredited to do CT scans by a certifying organization, such as the American College of Radiology
- Get scans read by an American Board of Radiology board-certified radiologist who is an expert in lung cancer screening
- Offer modern multislice CT equipment that does high-quality, low-dose, and non-contrast spiral CT
- Partner with a health center that has experience and excellence in biopsy methods, board-certified pulmonologists (lung doctors), and board-certified thoracic (chest) surgeons who are experts in lung cancer
What happens if a nodule is detected during screening?
A CT scan can detect lung abnormalities with great accuracy. However, it does not indicate whether the abnormality is malignant or benign. Doctors use the term pulmonary nodule to describe a specific type of abnormality that may suggest that further testing is required. A pulmonary nodule is defined as a small, approximately spherical, circumscribed focus of abnormal tissue that appears on the CT scan. It is typically less than 3 cm in diameter. Pulmonary nodules are associated with infectious and inflammatory diseases as well as with certain types of cancer, including lung cancer.11
Most nodules detected by CT scan are benign. If a pulmonary nodule(s) is/are detected, your doctor will decide whether you require additional tests or follow-up CT scans, based on the following:5
- Your medical history: Presence of any risk factors of lung cancer, family history of lung cancer
- Nodule characteristics: Size (nodules larger than 3 cm are typically considered cancerous unless a biopsy rules out cancer), location (nodules in upper lobes are more likely to be malignant), density (how well the x-rays from the CT scan pass through the nodule)
- How fast the nodule grows: The first CT scan is often referred to as a baseline scan. Your doctor may recommend that you get a CT scan after a few months to check how fast a nodule is growing
If no nodule is detected, the next scan is typically in 12 months.5
Latest research in lung cancer screening
Advances in imaging techniques, such as the low-dose CT scan, have improved the chances of finding lung cancer early. Researchers continue to look for other techniques that could help identify lung cancer at an early stage. More sensitive tests that can find lung cancer cells in sputum or blood, even before the cancer is seen on a CT scan, are being studied. In addition, biomarker testing to identify which patients have a higher risk of lung cancer is also being researched. Many medical centers, particularly academic centers, will ask their patients to participate in this research, as this is the only way to move our knowledge of this area forward.
Updated June 3, 2019
- SEER Stat Fact Sheets: Lung and Bronchus Cancer. National Cancer Institute website. http://seer.cancer.gov/statfacts/html/lungb.html. Updated April 2019. Accessed May 30, 2019.
- Lung Cancer Screening. RadiologyInfo.com website. https://www.radiologyinfo.org/en/info.cfm?pg=screening-lung. Revised August 10, 2018. Accessed May 31, 2019.
- Aberle, DR, Adams AM, et al. Reduced Cancer Mortality with Low-Dose Computed Tomographic Screening. N Engl J Med 2011; 365:395-409. doi: 10.1056/NEJMoa1102873. http://www.nejm.org/doi/full/10.1056/NEJMoa1102873#t=article. Published August 4, 2011. Accessed May 31, 2019.
- Lung Cancer Screening. . US Preventive Services Task Force website. http://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/lung-cancer-screening. Published December 2013. Accessed November 27, 2017.
- NCCN Guidelines for Patients®: Lung Cancer Screening, Version 1.2020. The National Comprehensive Cancer Network website. https://NCCN.org/patients/guidelines/lung_screening/files/assets/common/downloads/files/lungscreening.pdf. Posted May 14, 2019. Accessed May 30, 2019.
- Mazzone PJ, Silvestri GA, et al. Screening for Lung Cancer: CHEST Guideline and Expert Panel Report. CHEST Journal. April 2018. Volume 153, Issue 4, Pages 954-985. http://journal.chestnet.org/article/S0012-3692(18)30094-1/fulltext. Accessed May 31, 2019.
- Computed Tomography (CT) Scans and Cancer. National Cancer Institute website. http://www.cancer.gov/about-cancer/diagnosis-staging/ct-scans-fact-sheet. Reviewed July 16, 2013. Accessed May 31, 2019.
- CT scans. National Cancer Institute website. https://imaging.cancer.gov/imaging_basics/cancer_imaging/ct_scan. Updated December 22, 2016. Accssed May 31, 2019.
- National Lung Screening Trials: Questions and Answers. National Cancer Institute website. https://www.cancer.gov/types/lung/research/nlst.qa. Updated November 12, 2014. Accessed May 31, 2019.
- Terpennings S, Lin CT, White C. Lung Cancer Screening: Pros and Cons. Applied Radiology website. http://appliedradiology.com/articles/lung-cancer-screening-pros-and-cons. Published July 1, 2015. Accessed May 31, 2019.
- Asija A, et al. Pulmonary nodule: a comprehensive review and update. Hosp Pract (1995), 2014 Aug42(3): 7-16. doi: 10.3810/hp.2014.08.1125. https://www.ncbi.nlm.niih.gov/pubmed/25255402.