30-Second Summary
Lung cancer screening uses low-dose CT (LDCT), which involves less radiation than a standard CT scan.
It is recommended for people at increased risk because of a significant smoking history, not the general public.
The USPSTF recommends yearly LDCT for adults 50–80 with a 20 pack-year history who currently smoke or quit within 15 years.
A major trial found LDCT screening reduced lung cancer deaths by about 20% compared with chest X-ray.
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The full explanation.
The simple version
Lung cancer screening looks for lung cancer before it causes symptoms, using a special low-dose CT (LDCT) scan of the lungs. It isn't for everyone — NCI notes that the risk of lung cancer in people who have never smoked is generally so low that they'd be unlikely to benefit. Screening is aimed at people at increased risk because of a significant smoking history.
Who should be screened
The U.S. Preventive Services Task Force recommends annual low-dose CT screening for people who meet all of these:
- ages 50 to 80
- a 20 pack-year or more smoking history (for example, one pack a day for 20 years, or two packs a day for 10 years)
- currently smoke, or quit within the last 15 years
If you're unsure whether you qualify, your doctor can help you work out your pack-year history and eligibility.
The radiation involved
A low-dose lung CT uses an estimated 1.5 mSv of radiation — about the amount of natural background radiation a person receives in six months, and lower than a typical chest CT (about 6 mSv). For people at risk, that small exposure is weighed against the benefit of catching cancer early.
Benefits and harms
The benefit is significant: the National Lung Screening Trial found that three annual low-dose CT screens reduced lung cancer deaths by about 20% compared with chest X-ray.
But there are real harms to weigh:
- False positives — findings that look abnormal when no cancer is present. These need follow-up and can lead to invasive procedures to rule out cancer.
- Overdiagnosis — finding a cancer that would never have caused problems (though there's little evidence of this after long follow-up in the main trial).
- Incidental findings — because the scan also images organs outside the lungs, it may reveal other abnormalities, some serious and many not, that require follow-up.
A word about quitting
Screening does not remove the risk that comes from smoking, and it isn't a substitute for quitting. If you smoke, the single most powerful thing you can do for your lung health is to stop — and your care team can point you to resources to help. Screening and quitting work best together.
Words to know
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Common questions
▸What is lung cancer screening?
Lung cancer screening looks for lung cancer before symptoms appear, using a low-dose CT (LDCT) scan of the lungs. NCI notes that the risk of lung cancer in people who have never smoked is generally so low that they would be unlikely to benefit from screening, so it is aimed at people at increased risk because of their smoking history.
▸Who should be screened?
The U.S. Preventive Services Task Force recommends annual lung cancer screening with low-dose CT for people ages 50 to 80 who have a 20 pack-year or more smoking history and either currently smoke or quit within the last 15 years. A '20 pack-year' history could mean, for example, one pack a day for 20 years or two packs a day for 10 years.
▸How much radiation does a low-dose CT use?
The estimated effective dose of a low-dose lung CT is about 1.5 mSv — comparable to roughly 6 months of natural background radiation, and lower than a typical chest CT (about 6 mSv). Your care team weighs this small exposure against the benefit of screening for those at risk.
▸Does lung cancer screening save lives?
The National Lung Screening Trial found that three annual low-dose CT screens reduced lung cancer deaths by about 20% compared with chest X-ray. That benefit is why screening is recommended for people at higher risk — but it must be weighed against the potential harms.
▸What are the harms of lung cancer screening?
People screened with low-dose CT can have false-positive results — findings that look abnormal even though no cancer is present — which need monitoring and may lead to invasive procedures to rule out cancer. Overdiagnosis (finding a cancer that would not have caused problems) is possible. And because the scan also images areas outside the lungs, it can turn up incidental findings, some serious and many not.
Questions for your care team
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