Can non-small cell lung cancer be found early?
Usually symptoms of lung cancer do not appear until the disease is already in an advanced, non-curable stage. Even when symptoms of lung cancer do appear, many people may mistake them for other problems, such as an infection or long-term effects from smoking. This may delay the diagnosis.
Some lung cancers are diagnosed early because they are found as a result of tests for other medical conditions. For example, lung cancer may be found by imaging tests (such as a chest x-ray or chest CT scan), bronchoscopy (viewing the inside of lung airways through a flexible lighted tube), or sputum exam (microscopic examination of cells in coughed up phlegm) done for other reasons in patients with heart disease, pneumonia, or other lung conditions. A small portion of these patients do very well and may be cured of lung cancer.
Does screening for lung cancer save lives?
Screening is the use of tests or exams to detect a disease in people without symptoms of that disease. For example, the Pap test is used to screen for cervical cancer. Because lung cancer usually spreads beyond the lungs before causing any symptoms, an effective screening test for lung cancer could save many lives.
For many years, doctors have tried to see if a test to find lung cancer early would save lives. Studies of 2 possible screening tests, chest x-ray and sputum cytology, did find that these tests detected lung cancers at an early stage, but neither test helped patients live longer. This is why major medical organizations have not recommended routine screening with these tests for the general public or even for people at increased risk, such as smokers. Recently, though, a different lung cancer screening test has been shown to help lower the risk of dying from this disease.
Low-dose spiral CT
A type of CT scan known as low-dose spiral CT (or helical CT) has shown some promise in detecting early lung cancers in heavy smokers and former smokers. Spiral CT of the chest provides more detailed pictures than a chest x-ray and is better at finding small abnormalities in the lungs. The type used for lung cancer screening uses lower amounts of radiation than a standard chest CT and does not require the use of intravenous (IV) contrast dye.
The National Lung Screening Trial (NLST) is a large clinical trial that compared spiral CT scans to chest x-rays in people at high risk of lung cancer to see if these scans could help lower the risk of dying from lung cancer. The study included more than 50,000 people aged 55 to 74 who were current or former smokers with at least a 30 pack-year history of smoking (equal to smoking a pack a day for 30 years, or 2 packs a day for 15 years). Former smokers must have quit within the past 15 years. People were not eligible for the study if they had a prior history of lung cancer or lung cancer symptoms, or if they needed to be on oxygen at home to help them breathe.
People in the study got either 3 spiral CT scans or 3 chest x-rays, each a year apart. They were then observed for several years to see how many people in each group died of lung cancer.
The study found that people who got spiral CT had a 20% lower chance of dying from lung cancer than those who got chest x-rays. They were also 7% less likely to die from any cause than those who got chest x-rays, although the exact reasons for this are not yet clear.
Researchers are now analyzing the full results of the study, and there are some questions that still need to be answered. For example, it’s not clear if screening with spiral CT scans would have the same effect on different groups of people, such as those who smoked less (or not at all) or people younger than age 55. It’s also not clear what the best screening schedule might be (how often the scans should be done, how long they should be continued, etc.).
Spiral CT scans are also known to have some downsides that need to be considered. One drawback of this test is that it also finds a lot of abnormalities that turn out not to be cancer but that still need to be assessed to be sure. (About 1 out of 4 people in the NLST had such a finding.) This may lead to additional tests such as CT scans, or even more invasive tests such as needle biopsies or even surgery to remove a portion of lung in some people. A small number of people who do not have cancer or have very early stage cancer have died from these tests.
Spiral CT scans also expose people to a small amount of radiation with each test. It is less than the dose from a standard CT, but it is more than the dose from a chest x-ray. Some people who are screened may end up needing further CT scans, which is also a concern. When done in tens of thousands of people, this radiation will cause a few people to develop breast, lung, and thyroid cancers later on.
These factors, and others, need to be taken into account by people and their doctors who are considering whether or not screening with spiral CT scans is right for them.
Current screening recommendations
Although the American Cancer Society has not yet developed lung cancer screening guidelines, it has plans to do so in the future. In the meantime, some people who are at higher risk (and their doctors) may consider whether screening is appropriate for them.
While a full cancer screening guideline is being developed, the American Cancer Society has created interim guidance for people and their doctors regarding the use of low-dose CT scans for the early detection of lung cancer:
- People between the ages of 55 and 74 who meet the entry criteria of the NLST (see above) and are concerned about their risk of lung cancer may consider screening for lung cancer. With their doctor, people interested in screening should weigh the currently known benefits of screening with the currently known limits and risks in order to make a shared decision as to whether they should be screened for lung cancer.
- Doctors may choose to discuss lung cancer screening with their patients who meet NLST entry criteria.
- For people who do not meet the NLST entry criteria (because of younger age, smoking history, etc.), it is not clear if the possible benefits of screening outweigh the harms, so screening in these people is not recommended at this time. This is especially the case among people with no smoking history, in whom the possible harms are much more likely than benefits at this time. Whether people whose age or smoking history would have made them ineligible for the NLST should be screened will be addressed during the guidelines development process as more data becomes available.
- People who choose to be screened should follow the NLST protocol for annual screening. This should be done in an organized screening program at an institution with expertise in spiral CT screening, with access to a multidisciplinary team skilled in finding and treating abnormal lung lesions. Referring doctors should help their patients find institutions with this expertise.
- There is always benefit to quitting smoking. Active smokers entering a lung screening program should be urged to enter a smoking cessation program. Screening should not be viewed as an alternative to quitting smoking.
- For people considering screening (and their doctors), some statistics from the NLST may be helpful. Of the nearly 26,000 people screened by low-dose CT in the NLST, 1,060 were diagnosed with lung cancer. Screening is estimated to have prevented 88 lung cancer deaths while causing 16 deaths. Six of the 16 deaths were in patients who ultimately were found not to have cancer.
For more detailed information on the interim guidance, please see the American Cancer Society Interim Guidance on Lung Cancer Screening.
Even with the promising results from the NLST, people who are current smokers should realize that the best way to avoid dying from lung cancer is to stop smoking. For help quitting smoking, see our document called Guide to Quitting Smoking or call the American Cancer Society at 1-800-227-2345.
American Cancer Society Website