A low-dose computed tomography (low-dose CT) scan is a test that healthcare professionals use to screen for lung cancer. It works similarly to a regular-dose CT scan but emits much less radiation.

The earlier detection of lung cancer can mean more treatment options are available to a person and a higher chance of a positive outlook.

According to the Lung Cancer Foundation of America, the five-year survival rate for people who have received a lung cancer diagnosis before it has spread is 55%. For people with lung cancer that has spread, the five-year survival rate is 18%.

Survival rates refer to the number of people who are typically still alive, based on research, a number of years after they received a cancer diagnosis or started treatment for cancer.

Therefore, screening tests which detect the disease in people with no symptoms or history of the condition, such as low-dose CT (LDCT) scans, are important. Research shows yearly screenings using low-dose CT scans for people at a high risk of developing lung cancer help detect lung cancer early and save lives.

Read on to learn more about how LDCT scans detect lung cancer, including when doctors may recommend this test. We also discuss some associated risks and costs of LDCT.

A healthcare professional supervising someone undergoing a CT scan for lung cancer.Share on Pinterest
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The Centers for Disease Control and Prevention (CDC) recommend LDCT scans as the only screening test for lung cancer. This is because they are more reliable in showing lung tumors than a standard chest X-ray. They also produce more detailed images because an LDCT scan uses multiple radiation beams.

LDCT scans can show the tumor’s shape, size, and position and help find enlarged lymph nodes that may indicate the cancer has spread.

If an LDCT scan shows anything abnormal in a person’s lungs or nearby areas, doctors will perform further scans or other tests to determine the cause. Most abnormal findings will not be cancer, but doctors may still need to investigate to ensure they are benign.

Research shows that the higher a person’s risk of developing lung cancer, the more they benefit from screening.

The most important risk factor for developing lung cancer is tobacco smoking. According to the National Cancer Institute, tobacco smoking from cigarettes, cigars, and pipes causes around 9 in 10 lung cancer cases in males and around 8 in 10 in females.

The U.S. Preventive Services Task Force recommends yearly LDCT scans for people who fit all the following criteria:

  • are between 50 and 80 years old
  • smoke, or have quit smoking in the past 15 years
  • have a “20-pack-a-year” or more smoking history

Such people have a high risk of developing lung cancer. Experts do not currently recommend regular screening for other people as there is not enough evidence to suggest that it would benefit them.

Screenings are also most beneficial for people who do not have symptoms of lung cancer because the goal of screening is to detect cancer early before it spreads. Symptoms may indicate that the cancer has already spread. Symptoms of lung cancer include:

If a person experiences these symptoms, they should contact their doctor immediately.

Studies show that screening for lung cancer using LDCT scans reduces mortality rates by 20–24% due to their ability to detect cancers early.

A major advantage of LDCT scans is that they provide a high level of accuracy while exposing a person to as little radiation as possible. This is particularly helpful because a person with a high risk of the condition may require frequent testing. For this reason, doctors will usually screen a person using an LDCT rather than a regular CT scan.

The person will lie on a table that slides back and forth in the LDCT scanner. The scanner will emit a series of X-ray beams while rotating around the body, generating cross-sectional images. Together, these images create a detailed 3D image of the chest.

An LDCT scan is unlikely to be painful, and the appointment can take less than 30 minutes.

Furthermore, as part of the screening, doctors may provide other advice to help reduce a person’s risk of lung cancer. The American Cancer Society suggests that people who are having screening for lung cancer:

  • ask their doctor about the potential benefits, harms, and limitations of screening using LDCT scans
  • attend a center that has experience in lung cancer screening and treatment
  • attend counseling sessions to help them quit smoking if they currently smoke

Certain groups are less likely to benefit from screening. The CDC report that doctors stop yearly screenings when a person either:

  • has not smoked in the last 15 years (or more)
  • turns 81 years old
  • develops a health condition that means they are unable or unwilling to have surgery if the scan detects lung cancer

The CDC list three potential risks of LDCT scans:

False-positive results

A false positive occurs when a test suggests that a person has a condition or disease that they actually do not have.

The American Lung Association estimates that around 12–14% of initial screenings for lung cancer produce a false positive. One 2021 study found that the likelihood of receiving a false positive could reduce with each subsequent screening round.


LDCT screening for lung cancer may sometimes result in overdiagnosis, meaning that it can detect tumors that will not cause the person harm in their lifetime. This may lead to unnecessary cancer treatment, its potential side effects, and distress that would not have occurred if the person did not have the scan.

Radiation from repeated LDCT tests

An LDCT scan involves a person undergoing exposure to a small, targeted amount of radiation. While regular CT scans provide 7 millisieverts (mSv) of radiation, an LDCT scan provides 1.4 mSv. The Food and Drug Administration (FDA) notes that the potential associated risk of developing fatal cancer due to a CT scan providing 10 mSv is less than 1 in 2,000.

A person’s doctor will ensure that the benefits outweigh the risks when recommending that they have an LDCT scan.

The cost of LDCT scans can vary depending on the person’s location and the institution offering the scan. Most United States facilities charge between $100 and $400.

Most insurance plans and Medicare can help a person pay for screening tests for lung cancer that a doctor has recommended, the CDC note. A person should check with their plan to find out exactly what their cover includes.

If a person does not have health insurance, they should check with their local health department to see if any programs are available to help them. The American Lung Association provides general information on insurance coverage for lung cancer screenings.

Annual LDCT scans can increase the chances of survival for people who are at a high risk of developing lung cancer. These imaging tests use a lower amount of radiation than traditional CT scans.

Early detection by LDCT scans can help a person get the treatment they need before cancer spreads. If a person is at a high risk of developing lung cancer, they should ask their doctor about screenings.