Lung Cancer Screening

Screening is testing done before any symptoms arise. The purpose of screening is to catch cancer in its earliest stages. Lung cancer causes more deaths than any other type of cancer. This is in part because it is often found after it has spread. The earlier a cancer is found, the greater the chance of successful treatment.

Risk factors for lung cancer

There are several factors that increase a person’s risk for lung cancer. Some of these are controllable, while others are uncontrollable. Risk factors include, but are not limited to:1

  • Smoking
  • Secondhand smoke exposure
  • Exposure to radon
  • Exposure to asbestos or other workplace carcinogens (substances that can increase the risk of developing cancer)
  • Family history of lung cancer
  • Previous radiation therapy to the breast or chest
  • Air pollution

Who should be screened?

There are several national groups that have similar screening guidelines. Screening recommendations are based on groups of people who fit certain criteria. Risk groups are broken into different categories, including higher versus lower risk.

In 2021, the United States Preventive Services Task Force (USPSTF) updated their guidelines for lung cancer screening.

According to the task force, yearly screening is recommended for people between the ages of 50 and 80 years old who have a 20 pack-year (or more) smoking history. The guidelines apply to both current smokers and people who have quit smoking in the past 15 years.2,3

The term pack-years is used to help determine a person’s history of smoking. It is calculated by multiplying the number of packs of cigarettes smoked per day by the number of years the person has smoked. For example, smoking 1 pack per day for 1 year equals 1 pack-year. Smoking 2 packs per day for 10 years equals 20 pack-years. Smoking half a pack per day for 10 years is 5 pack-years. In these estimates, 1 pack has 20 cigarettes.1,2

Screening tools

Those at high risk for lung cancer can be screened using a low-dose computed tomography (LDCT) scan of the chest. LDCT takes several X-ray pictures of the body using different angles. This creates a 3-dimensional picture with good detail. While LDCT uses X-ray imaging, the amount of radiation is lower than standard a CT (computed tomography) scan. This is 1 test available for screening and reducing the number of deaths from lung cancer.2,3

With LDCT, there is still a potential risk of “false positive” results. This is when a test suggests there is cancer but no cancer is actually present. A false positive can lead to additional unnecessary tests, procedures, and anxiety.2,3

Screening results

The LDCT looks for nodules in the lungs. Nodules are small, round masses of tissue. These can be caused by cancer, infections, scar tissue, or other conditions. Nodules caused by cancer appear differently on LDCT than nodules that are not cancerous (benign). Cancerous nodules generally have rough edges and more unusual shapes. They also grow quickly and are often larger in size than benign nodules.2

The American College of Radiology has created a grouping system that can be used when doctors are looking at LDCT scans. The system, called the Lung Imaging Reporting and Data System (Lung-RADS), can help separate cancerous from non-cancerous nodules. This reduces the risk of false positives. Nodules that are suspicious for cancer may lead to further imaging, biopsies, or surgery.2

The first LDCT used in screening identifies nodules that are present in the lungs, whether cancerous or not. This scan is considered the baseline for future tests. Doctors use it as a comparison to note any changes in size or appearance of nodules in future scans.2

Making the decision to be screened

There are benefits and risks of lung cancer screening. Recommendations like those made by the USPSTF are meant to guide screening decisions. However, other organizations have different screening recommendations as well.

The decision on whether or not to be screened is not a perfect science. Some people may fall into the group suggested by the USPSTF and feel comfortable getting screened. Others may not meet these criteria but have other additional risk factors or concerns.

As mentioned, the USPSTF guidelines are for those aged 50 to 80 years who are current smokers or those who have quit in the past 15 years. Others outside of this window have less clear guidance. Further, some may benefit from yearly screening, while others might benefit from less frequent scans. There are many issues to consider and often no single best answer.2,3

Talking with a doctor about your specific risk factors and concerns can be helpful. Together, you can weigh the risks and benefits to determine if screening is right in your situation.

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Written by: Emily Downward and Casey Hribar | Last reviewed: March 2021