Substantial reduction in lung cancer mortality using volume CT screening: the NELSON trial
Years ago, the large National Lung Screening Trial that was published in 2011 demonstrated a 20 % relative reduction in lung cancer mortality due to annual screening over 3 years with low-dose CT compared to chest radiography . However, no other randomised, controlled trial has shown any mortality benefits to date.
In the Netherlands and Belgium, the randomised, controlled NELSON trial compared volume CT screening vs. no screening in high-risk individuals who were recruited through population-based registries . Out of 606,409 men and women aged 50-74 years, 30,959 were found to be eligible based on questionnaires. They had a smoking history of > 10 cigarettes/day for > 30 years or > 15 cigarettes/day for > 25 years. Also, smoking cessation during the last 10 years was an inclusion criterion. Eventually, 15,792 persons entered the screen arm (n = 7,900) or the control arm (n = 7,892). More than 80 % were males, with a median age of just under 60 years and approximately 40 pack years. A little more than half were current smokers. Volume and volume doubling time of nodules were used for measurements. Screening took place at 1 year, 2 years, 4 years, and 6.5 years. Acceptance was high for several years and decreased only later on.
In the course of all of the 4 rounds, indeterminate test results were found in 9.3 %. The study showed a referral rate for further investigation as low as 2.3 %. Ultimately, the rate of positive results was 2.2 %, leading to a lung cancer detection rate of 0.9 %. This corresponded to a 41 % probability of lung cancer detection in case of a positive result (i.e., positive predictive value). According to the stage distribution analysis, screening gave rise to a massively higher detection rate of stage Ia tumours compared to the later stages, which contrasted with the findings in the control arm that matched those in the Dutch Cancer Registry.
At year 10, the lung cancer mortality rate ratio was 0.74 in males (p = 0.003) and 0.61 in females (p = 0.0543); thus, volume CT screening had reduced the lung cancer-related risk of dying by 26 % in men and by 39 % in women. While the risk reduction proved stable in men, women showed consistently better results with risk reductions of 61 % and 53 % at years 8 and 9, respectively. Overall, these results were more favourable than the NLST findings and demonstrated a substantial reduction in lung cancer mortality in both genders.