Participants were randomized 1:1 in a screening and control group. Subjects who were selected for screening were periodically invited to undergo low dose computed tomography (CT) scans from the chest. Both groups (the screen participants and the controls) filled out questionnaires at the start of the trial and at the follow up after 10 years.
More specifically, the population comprised of people born between 1928 and 1956 originating from the Netherlands and Belgium, who:
• Smoked > 15 cigarettes/day during > 25 years,
• Or smoked > 10 cigarettes/day during > 30 years,
• and were current smokers or former smokers who quit smoking ≤ 10 years ago.
Excluded were those with a moderate or bad self-reported health who were unable to climb two flights of stairs, those with a body weight ≥ 140 kg, with current or past renal cancer, melanoma or breast cancer, or with lung cancer diagnosed less than 5 years ago, or 5 years or more ago but still under treatment. Also those who had a chest CT examination less than one year before they filled in the first NELSON questionnaire were excluded.
Participants from the screening group were invited for a diagnostic test at years 1, 2, 4, and 6 , as shown in the figure. No scans were made in the control group as part of the trial.
Screen test results that were indeterminate [a] resulted in a short-term follow-up CT screening 3-4 months later (not shown in the figure).
[a]: Oval-shaped growths in the lungs are called lung nodules. Depending on the nodule’s shape, size, and texture this abnormal growth of tissue can be potentially cancerous (malignant). To determine the outcome of the test, the diameter d, the volume V, and the doubling time 𝜏 of the nodules are compared to criteria outlined in Table 1 in Ref. .
: H. J. de Koning et al. "Reduced lung-cancer mortality with volume CT screening in a randomized trial." N. Engl. J. Med. 382.6 (2020): 503-513.
: Y. R. Zhao et al., NELSON lung cancer screening study, Cancer Imaging 11, S79 (‘11).
: D. M. Xu et al., Nodule management protocol of the NELSON randomised lung cancer screening trial, Lung Cancer 54, 177 (‘06).