NLST & NELSON (low-dose CT screening)
The two trials that proved a yearly low-dose CT scan cuts lung cancer deaths in heavy smokers.
NLST (NEJM 2011) showed a 20% relative reduction in lung cancer mortality with three annual low-dose CTs versus chest radiography. NELSON (NEJM 2020) showed a 24% reduction in men at 10 years with volume-based nodule management and a lower false-positive rate. Together they underpin USPSTF (age 50-80, ≥20 pack-years) and European screening recommendations. Uptake remains low.
- 20 out of 100 people alive with Low-dose CT vs chest X-ray.
- 24 out of 100 people alive at 10 years with Low-dose CT vs no screening.
- There was no comparison group, so this number cannot tell you how much of the effect is due to the treatment.
- Overall survival counts deaths from any cause, so it is the most direct measure of whether a treatment helps people live longer.
- These results apply to the people the trial enrolled: Annual low-dose CT versus chest X-ray (NLST, 53,454 heavy smokers) or no screening (NELSON, 15,789) in current and former smokers. People in a different situation may not see the same effect.
Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.
53,454 participants enrolled.
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| NLST: relative reduction in lung cancer mortalityprimary | Low-dose CT vs chest X-ray | — | 20% | — | — | link |
| NELSON: relative reduction in lung cancer mortality at 10 years (men)primary | Low-dose CT vs no screening | — | 24% | — | — | link |
Lung screening works when it uses volumetric nodule management, and it works against a no-screening control. The protocol underpins the UK Targeted Lung Health Check programme and European recommendations. Benefit in women remains less precisely estimated.
For people with a heavy smoking history, an annual low-dose CT scan is one of the few screening tests proven to reduce cancer deaths. Most abnormal scans are not cancer, so screening must be paired with careful nodule management. It does not apply to never-smokers or light smokers.