Low-dose CT lung cancer screening: who's actually eligible and why the criteria are so specific

Current USPSTF guidelines recommend annual low-dose CT lung cancer screening for adults aged 50-80 with a significant smoking history — commonly expressed in pack-years, a measure combining intensity and duration — who currently smoke or quit within the past 15 years. The specificity of these criteria isn't arbitrary; it reflects trial data (notably the National Lung Screening Trial) establishing the population in which screening's mortality benefit outweighs the harms of false positives and incidental findings requiring follow-up.

That risk-benefit balance is the key reason screening isn't recommended more broadly — low-dose CT has a real false-positive rate, and in a lower-risk population, the cumulative harm from unnecessary follow-up procedures for benign findings can outweigh the benefit of catching the relatively few cancers that would actually be present in that lower-risk group.

For people who quit smoking more than 15 years ago or who fall outside the pack-year threshold, that doesn't mean lung cancer risk is zero — it means the population-level screening math doesn't favor routine CT screening for that specific group, which is a distinct statement from individual risk. Anyone with respiratory symptoms warranting evaluation should still be seen regardless of screening eligibility criteria.