Accepted on 06 Sep 2019
Submitted on 30 Aug 2019
The NELSON study or “NEderlands Leuvens Longkanker Screening ONderzoek” is a Dutch-Belgian Randomized Lung Cancer Screening Trial. This trial was designed to investigate whether screening for lung cancer by low-dose multidetector computed tomography (CT) in high-risk subjects will lead to a decrease in 10-year lung cancer mortality of at least 25% compared with a control group without screening. During the IASLC 19th World Conference on Lung Cancer in Toronto in September 2018, the final results of this study were presented. The Nelson study showed a reduced risk of dying from lung cancer of 26% in the screen arm compared to the control arm for man at high risk for lung cancer. For woman these results were even better. In women there was a reduced risk of dying from lung cancer of 39–61%. These results are more favorable than the NLST results and suggest gender differences. The conclusion at the congress was that there is now conclusive evidence for implementation of Lung cancer screening (in Europe), based on two large RCT’s, the NLST and the Nelson trial. The question is now: is everyone ready to do this?
The Nelson study is a randomized Lung Cancer screening trial using low dose CT. In this study the setting of low dose CT is well defined (Table 1). The dose of this low dose chest CT is 1.13 mSv. The comparable doses of a chest X-ray and diagnostic chest CT are respectively 0.02 and 7.07 mSV.
Table 1
CT doses in the Nelson study.
| Body weight | kVp settings | CTDIvol |
|---|---|---|
| <50 kg | 80–90 kVp | 0,8 mGy |
| 50–80 kg | 120 kVp | 1,6 mGy |
| >80 kg | 140 kVp | 3,2 mGy |
In the Nelson study nodule categorization is based on size and characteristics for new nodules and on growth rate for existing nodules (Table 2). Management of the nodules is based on these categories (Table 3).
Table 2
Nodule categorization based on size and characteristics (new nodules) and growth rate (existing nodules) in Nelson Study.
| Category | Definition | ||
|---|---|---|---|
| NODCAT 1 | A benign nodule (with fat benign calcifications) or other benign abnormalities | ||
| NODCAT 2 | A nodule, smaller than NODCAT 3, not belonging to NODCAT 1 | ||
| Solid | Partial solid | Non-solid | |
| NODCAT 3 | 50 ≤ V ≤ 500 mm3 | Solid component: 50 ≤ V ≤ 500 mm3 | dmean ≥ 8 mm |
| Pleural based: 5 ≤ dmin ≤ mm | Non-solid component: dmean ≥ 8 mm | ||
| NODCAT 4 | V > 500 mm3 | Solid component: V > 500 mm3 | Non-existent category |
| Pleural based: dmin > 10 mm | |||
| GROWCAT A | VDT > 600 days | ||
| GROWCAT B | 400 ≤ VDT ≤ 600 days | ||
| GROWCAT C | VDT < 400 days, or new solid component in non-solid lesion | ||
V, volume; dmin, minimal diameter; dmean, mean diameter; VDT, volume-doubling time.
Zhao Y et al. Cancer Imaging 2011 Oct 3, 11.
Table 3
Nelson management protocol for non-calcified pulmonary nodules in the different screening rounds.
| Year 1 | Year 2 | Year 4 | Year 6 | |
|---|---|---|---|---|
| NODCAT 1 | Negative test | Negative test | Negative test | Negative test |
| Annual CT | CT in year 4 | CT in year 6 | End of screening | |
| NODCAT 2 | Negative test | Indeterminate test | Indeterminate test | Indeterminate test |
| Annual CT | CT after 1 year | CT after 1 year | End of screening | |
| NODCAT 3 | Indeterminate test | Indeterminate test | Indeterminate test | Indeterminate test |
| 3 months follow-up CT | CT after 6–8 weeks | CT after 6–8 weeks | CT after 6–8 weeks | |
| NODCAT 4 | Positive test | Positive test | Positive test | Positive test |
| Refer to pulmonologist for work-up and diagnosis | Refer to pulmonologist for work-up and diagnosis | Refer to pulmonologist for work-up and diagnosis | Refer to pulmonologist for work-up and diagnosis | |
| GROWCAT A | Negative test | Negative test | Negative test | Negative test |
| CT in year 2 | CT in year 4 | CT in year 6 | End of screening | |
| GROWCAT B | Negative test | Indeterminate test | Indeterminate test | Indeterminate test |
| CT in year 2 | CT after 1 year | CT after 1 year | CT after 1 year | |
| GROWCAT C | Positive test | Positive test | Positive test | Positive test |
| Refer to pulmonologist for work-up and diagnosis | Refer to pulmonologist for work-up and diagnosis | Refer to pulmonologist for work-up and diagnosis | Refer to pulmonologist for work-up and diagnosis | |
Zhao Y et al. Cancer Imaging 2011 Oct 3, 11.
The Nelson study proved that it is possible to screen for lung cancer with low dose CT. From technical point of view these CT examinations can be performed anywhere. Reading of these CT examinations should be done following the same procedure and using the same software. Unfortunately for the moment there is no consensus about this. There are also many other open questions: who will lead this project? who will be screened? who will read these examinations? first reader? second reader? consensus reading? who is responsible for the follow-up of the patients? And maybe the most important question: who will pay for it?
(No information provided)