Lung Cancer Screening: Who Qualifies and How the Low-Dose CT Scan Works

What it involves

The CDC defines screening as testing for a disease when there are no symptoms or history of that disease, with the aim of finding it early when treatment may work better. For lung cancer the recommended test is a low-dose CT scan, which uses a small amount of radiation to make detailed pictures of the lungs.

Who this is for

• Current smokers between 50 and 80 who have smoked a pack a day for 20 years, or the equivalent
• Former smokers in that age range who quit within the past 15 years
• Patients unsure how to count their own pack-years and wanting help working it out
• Smokers who are not eligible for screening but want help quitting and a check on lung symptoms

What to expect

• A review of your smoking history, how many years and how much per day, to see whether you meet the screening criteria
• A talk about the benefits and the risks of screening, so the decision is yours and informed
• A referral to a screening facility for the scan if you qualify and decide to go ahead
• A separate visit, if you have a new cough or other symptoms, because symptoms are not screening

The three questions that decide eligibility

The CDC says the US Preventive Services Task Force recommends yearly screening with a low-dose CT scan for people who meet all three conditions at once: a smoking history of 20 pack-years or more, currently smoking or having quit within the past 15 years, and being between 50 and 80 years old. If one of those is missing, the recommendation does not apply. Eligibility is therefore a matter of arithmetic and honest history, which is why the first part of the visit is simply a conversation about how long and how much you smoked.

Working out your pack-years

A pack-year, according to the CDC, means smoking an average of one pack of cigarettes per day for one year. A person could reach 20 pack-years by smoking one pack a day for 20 years or two packs a day for 10 years. The arithmetic can land on either side of the line: someone who smoked lightly for decades may fall below it, while someone who cut back long ago may still qualify. Bring your best memory of when you started, when you quit if you did, and the usual number of cigarettes each day.

What the scan is like

The CDC describes the low-dose scan this way: you lie on a table while an x-ray machine uses a small amount of radiation to make detailed images of your lungs. It takes a few minutes and does not hurt. The test is done at a screening facility rather than during a primary care office visit, and a provider arranges the referral. The CDC adds that the American College of Radiology offers a locator tool for finding a screening program near you.

The benefit and the three risks

The CDC says that screening people at high risk can reduce deaths by finding lung cancer early, when treatment works best. It is equally direct about the downsides. A scan can suggest cancer when none is present, called a false positive, which may lead to follow-up tests and procedures that were not needed. Screening can also find cancers that might never have caused a problem, called overdiagnosis. And radiation from repeated scans can itself cause cancer in otherwise healthy people. That balance is why the CDC says to talk with a doctor first.

When screening stops

The Task Force recommends that yearly screening stop when the person turns 81, when they have not smoked in 15 or more years, or when they develop a health problem that makes them unwilling or unable to have surgery if cancer were found. Those exits are part of the same honest weighing of benefit against risk. Someone who is no longer a candidate is not being dismissed. Their lungs are still worth watching, and a persistent symptom deserves its own visit, such as the one described in the persistent cough guide.

Insurance, symptoms and quitting

The CDC says most insurance plans and Medicare help pay for recommended lung cancer screening, though follow-up tests after an abnormal result may carry a copay or deductible, so it suggests checking with your plan. It also separates screening from symptoms: screening is for people who feel fine. Coughing up blood, unexplained weight loss or new breathlessness is a different situation, and the shortness of breath guide explains what to do. For anyone who still smokes, quitting remains the single most useful step.

Sources

• CDC — Screening for Lung Cancer
• MedlinePlus — Lung Cancer