Who this is for
Eligibility turns on three numbers, and all three bodies use the same three: your age, your pack-years, and, for two of the three, how long ago you quit.
A pack-year is one pack a day for one year. Two packs a day for ten years is 20 pack-years, and so is one pack a day for twenty years.
Screening is for people with no symptoms. A cough that will not clear, coughing blood, chest pain or unexplained weight loss is a reason to be evaluated now. That is diagnosis, not screening, and eligibility rules do not apply to it.
All three bodies also say screening is not for you if a serious health problem means you could not have, or would not want, surgery or treatment for a cancer that was found.
Where the recommendations diverge
- USPSTF 50 to 80
- ACS 50 to 80
- ACCP 55 to 77
- ACCP 50 to 80
The USPSTF recommends annual screening for lung cancer with low-dose computed tomography (LDCT) in adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years.
Our note: The next sentence of the same recommendation is the stop rule and is why the 15-year clock matters: "Screening should be discontinued once a person has not smoked for 15 years or develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery." The statement says on its own page that it widened the range: previously 55 to 80 years and 30 pack-years.
The American Cancer Society recommends yearly screening for lung cancer with a low-dose CT (LDCT) scan for people ages 50 to 80 years who: Smoke or used to smoke AND Have at least a 20 pack-year history of smoking
Our note: One sentence with two criteria set as bullets on the page. The bullet markers are dropped and the two criteria are run inline; the word AND sits on its own line between them on the page, and is kept. Nothing is added. There is no years-since-quitting criterion anywhere on this page: ACS removed it in 2023 (see the disagreement note below).
For asymptomatic individuals age 55 to 77 who have smoked 30 pack years or more and either continue to smoke or have quit within the past 15 years, we recommend that annual screening with low-dose CT should be offered (Strong Recommendation, Moderate-Quality Evidence).
Our note: Published by the American College of Chest Physicians as CHEST Guideline and Expert Panel Report. Its own grade is "Strong Recommendation, Moderate-Quality Evidence"; the grade cell holds the short form only. CHEST's own remark on this row: "These eligibility criteria align with the eligibility criteria for CMS coverage at the time of publication." DATE CONVENTION: the article page prints only the issue month, November 2021, so the first of that month is used; its own metadata records an online-first date of July 13, 2021.
For asymptomatic individuals who do not meet the smoking and/or age criteria in Recommendation #1, are age 50 to 80, have smoked 20 pack years or more and either continue to smoke or have quit within the past 15 years, we suggest that annual screening with low-dose CT should be offered (Weak Recommendation, Moderate-Quality Evidence).
Our note: CHEST's own remark: "These criteria align with the 2021 recommendations from the USPSTF." A third recommendation extends an offer of annual screening to people outside both bands who are projected to have a high net benefit on a validated risk or life-years-gained calculator. DATE CONVENTION: same as the row above, the page prints only November 2021 and the first of the month is used.
Why they differ
On paper these three look close. In a clinic they are not, and the gap is about one thing: how long ago you quit.
- USPSTF (2021) and CHEST / ACCP (2021) both stop your eligibility once you have been smoke-free for 15 years. USPSTF states it as a discontinuation rule inside the recommendation itself.
- ACS (guideline page revised January 2024) has no years-since-quitting criterion at all. Its own announcement of the change, dated November 1, 2023, says so in one sentence: "The most important change in the updated guideline is that the number of years since quitting smoking is no longer a qualifier for starting or stopping yearly screening."
ACS published its reasoning: "These changes mean that many people who started screening will not lose eligibility by reaching 15 years since they quit. This is important because their risk of lung cancer is still rising due to increasing age." The same announcement adds that people with a 20 pack-year history who reach 15 years since quitting before age 50 "will now be eligible to start and continue screening."
The second gap is CHEST's two-tier structure. Its strong recommendation is the older, narrower band, 55 to 77 and 30 pack-years, and the remark CHEST attaches to it reads: "These eligibility criteria align with the eligibility criteria for CMS coverage at the time of publication." The 50 to 80 and 20 pack-year band that USPSTF and ACS both use is only a weak recommendation in CHEST's scheme, and its remark there reads: "These criteria align with the 2021 recommendations from the USPSTF." So a person aged 52 with 22 pack-years is squarely recommended by two bodies and merely suggested by the third.
CHEST also draws a hard line the other two do not: for people under 50, over 80, below 20 pack-years or more than 15 years quit who do not score well on a risk calculator, it says low-dose CT screening should not be performed, and grades that strongly.
3 documents set the numbers on this page. The oldest was published in 2021, the newest in 2024.
- https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/lung-cancer-screening
- https://www.cancer.org/cancer/types/lung-cancer/detection-diagnosis-staging/detection.html
- https://journal.chestnet.org/article/S0012-3692(21)01307-6/fulltext
We last re-read these sources on . How we verify.
What the test involves
You lie on a table that slides through the ring of a CT scanner. Nothing is injected and nothing has to be swallowed. The scan itself takes a few minutes; the whole visit is usually under half an hour. Radiation is lower than a standard CT and higher than a chest x-ray.
All three bodies attach conditions to where it is done and what happens first. ACS says screening should only be done at facilities with the right scanner, experience in low-dose CT, and a team that can follow up abnormal results. CHEST asks programs to check for symptoms before the scan, so that someone who should be getting a diagnostic work-up is not put through a screening pathway instead. Both, and USPSTF, expect a counselling and shared-decision conversation first.
If the result is abnormal
Most abnormal findings are not cancer. A nodule usually means more scans on a set schedule to see whether it grows; a minority lead to a biopsy or surgery, which carry real risks. ACS puts the trade honestly: screening will not find every lung cancer, and some cancers it does find will still be fatal.
Screening is not an alternative to stopping. Every one of these bodies pairs the scan with cessation support, and USPSTF and CHEST both build counselling into the screening visit itself.
More on this screening
Frequently asked questions
I quit 18 years ago. Am I eligible?
It depends whose rule your clinician is using, and this is the single biggest disagreement on this page. Under USPSTF and CHEST you are not: both stop eligibility at 15 smoke-free years. Under the American Cancer Society you are, provided you are 50 to 80 with at least a 20 pack-year history, because ACS removed years-since-quitting from its criteria in 2023. Insurance follows coverage rules, not guidelines, so ask what your plan uses.
How do I work out my pack-years?
Packs per day multiplied by years smoked. One pack a day for 20 years is 20 pack-years. Half a pack a day for 40 years is also 20. Two packs a day for 10 years is 20 again. ACS states the arithmetic on its own page in exactly these terms.
Is a chest x-ray a reasonable substitute?
No. ACS addresses this directly: chest x-rays have been studied as a screening test for people at higher risk and have not been shown to help most people live longer, so they are not recommended for lung cancer screening. Low-dose CT is the only test with trial evidence behind it.
Why does CHEST grade the 50 to 80 band only weakly?
CHEST publishes two bands. The strong one, 55 to 77 with 30 pack-years, carries CHEST's own remark that "These eligibility criteria align with the eligibility criteria for CMS coverage at the time of publication." The wider band, 50 to 80 with 20 pack-years, is graded weak, and its remark says "These criteria align with the 2021 recommendations from the USPSTF." CHEST states the concordance in both cases; it does not say either band was written in order to match those criteria. Weak in the GRADE system does not mean doubtful; it means the balance of benefits and harms is closer, so the individual's own preferences carry more weight.