NELSON: Low-dose CT screening reduces lung cancer mortality
medwireNews: Individuals at high risk for developing lung cancer benefit from periodic screening with low-dose computed tomography (CT), indicate the 10-year results from the NELSON trial.
Lung cancer mortality rates were significantly lower among participants who did versus did not undergo CT screening, says the research team in The New England Journal of Medicine.
The investigators note that their results are similar to those of the US-based National Lung Screening Trial (NLST), which showed a reduction in lung cancer mortality with three rounds of annual CT screening versus chest radiography.
In light of the NLST and NELSON results, the authors of an accompanying editorial remark that “[o]ur job is no longer to assess whether low-dose CT screening for lung cancer works: it does.”
Stephen Duffy (Queen Mary University of London, UK) and John Field (University of Liverpool, UK) continue: “Our job is to identify the target population in which it will be acceptable and cost-effective.”
The Dutch–Belgian NELSON trial included 15,792 individuals (13,195 men and 2594 women) considered at high risk for lung cancer due to being current or former (quit ≤10 years) smokers who smoked more than 15 cigarettes a day for over 25 years or more than 10 cigarettes a day for more than 30 years. Participants either underwent four rounds of low-dose CT screening, at intervals of 1, 2, and 2.5 years, or no screening as per the random assignment.
After 10 years of follow-up, the cumulative incidence of lung cancer in the primary analysis group, which comprised the male participants, was higher in the screening arm than in the control arm, at 5.58 versus 4.91 cases per 1000 person–years, and the incidence of lung cancer mortality was lower, at 2.50 versus 3.30 deaths per 1000 person–years.
This equated to a significant cumulative rate ratio for lung cancer mortality of 0.76 at 10 years, favoring the screening group.
All-cause mortality rates, however, were comparable between participants who did and did not undergo screening, at 13.93 and 13.76 deaths per 1000 person–years.
In terms of lung cancer mortality, there was a similar benefit amongst the subgroup of women participants, with a rate ratio for death from lung cancer of 0.67 at 10 years.
This suggests “a greater relative benefit in women than in men,” which was also observed in the NLST and other research, say the editorialists, adding that “[f]urther examination of this question is needed in the results of the other European trials to ascertain whether this is a general phenomenon and, more importantly, why it occurs.”
In all, 9.2% of participants needed at least one additional scan to confirm tumor growth or regression, with the proportion highest at baseline, at 19.7%, before decreasing to between 1.9% and 6.7% from year 1.0 to 5.5.
Finally, Harry de Koning (Erasmus Medical Center, Rotterdam, the Netherlands) and fellow NELSON investigators report that at the 10-year mark, the excess-incidence overdiagnosis rate among the male participants was 19.7%, but this decreased to 8.9% when follow-up was extended to 11 years.
“This is in line with modeling analyses suggesting that the lead time of CT screening can be as long as 9 to 12 years for some cancers, which indicates that appropriate estimation of the level of overdiagnosis in the NELSON trial requires additional years of follow-up,” they write.
Commenting on these data, Duffy and Field highlight the “considerably smaller numbers of overdiagnoses than of lives saved,” and conclude: “Although there is no room for complacency in this regard (there is no ‘good’ way to receive a diagnosis of lung cancer), the balance of overdiagnosis and mortality reduction is likely to be acceptable.”
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