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Results of the National Lung Screening Trial (NLST) are in!
Enrollment was 8/2002 to 4/2004. Follow-up was through end of 2009. Patients were age 55-74, with >30 pack-year smoking history, still smoking or quit <15 years. Intervention / Control: Low-dose chest CT vs. chest plain films thrice-yearly.
By screening these 53,454 high-risk people, 62 deaths per 100,000 person-years were prevented (247 vs. 309; relative risk reduction of 20%). A full 39% of those screened had at least one positive/abnormal CT scan. One-quarter of all CT scans were abnormal, and 96% of those were false-positives. The number needed to screen with CT to prevent one lung cancer death was 320. (n=53,454)
Complications from invasive diagnostic evaluation:
About 1.5% of participants were affected overall (but out of 53,454 that's more than 8,000 people). For those who ultimately did not have cancer, abnormal scans led to a major complication from an invasive procedure only 0.06% of the time. (But 11% of the scans ultimately found to show cancer were associated with a major complication.) Twenty-six people died within 60 days after an invasive procedure (causality unclear); 20 of the 26 had lung cancer.
Some overdiagnosis is strongly believed to have occurred in the NLST, although overdiagnosis (by definition) cannot falsely account for the mortality benefit observed. An estimated 10-15 years must pass before the extent of stage-shift (overdiagnosis through detection of early stage cancers that would never invade or become lethal) that occurred in NLST can be determined.
Implementation of Lung Cancer Screening CT
Since publication, discussion has shifted to implementation in the general public, with the American Lung Association recommending lung cancer screening CTs, but the American Thoracic Society and American College of Chest Physicians more cautiously endorsing lung cancer screening CT and warning of potential risks.
Risk stratification of patients using available lung cancer risk calculators, and possibly restricting lung cancer screening CT to patients at the highest risk for lung cancer, have been proposed as possible strategies to successfully implement lung cancer screening CT in the general U.S. population and in other developed countries.
NLST published results: NEJM 2011;June 29 online.
Editorial by Harold Sox: Better Evidence about Screening for Lung Cancer. N Engl J Med 2011;365:455-457.
Basis for stopping the NLST early: (cancer.gov)