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C. Van Der Aalst



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    ORAL 09 - CT Screening - New Data and Risk Assessment (ID 95)

    • Event: WCLC 2015
    • Type: Oral Session
    • Track: Screening and Early Detection
    • Presentations: 1
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      ORAL09.02 - Results of the Fourth Screening Round of the NELSON Lung Cancer Screening Study (ID 1354)

      10:45 - 12:15  |  Author(s): C. Van Der Aalst

      • Abstract
      • Presentation
      • Slides

      Background:
      Although screening can reduce lung cancer (LC) mortality, the optimal screening strategy (e.g. numbers of screening rounds, screening interval) is unclear. The use of different screening intervals in the NELSON study is unique and makes it possible to investigate how the screening test performances (e.g. lung cancer detection rate, false positive rate) and characteristics of screen-detected lung cancers might change. This study describes the results of a fourth screening round that took place 2.5 years after the third round.

      Methods:
      The Dutch-Belgian randomized-controlled Lung Cancer Screening Trial (NELSON) aims to investigate whether low-dose CT screening would reduce LC mortality by at least 25% relative to no screening after ten years of follow-up. Therefore, screen group participants were screened four times: at baseline and year 1, 3, and 5.5. Screening test results were classified as negative, indeterminate, or positive based on nodule presence, volume (in case of new nodules) and volume doubling time (in case of previous existing nodules). Participants with an indeterminate test result underwent follow-up screening to classify their final screening test result as positive or negative. Participants with a positive scan result were referred to a pulmonologist for a diagnostic work-up. For this study, we included only participants who had attended all four screening rounds (n=5279). Epidemiological, radiological and clinical characteristics of lung cancers detected in the fourth round were compared with those of the lung cancers detected in the first three rounds. In addition, the risk for lung cancer detection in the fourth round (5.5 year risk) was quantified for subgroups.

      Results:
      In round four, 46 lung cancers were detected; 58.7% were diagnosed at stage I, 15.2% at stage II and 23.8% at stage III/IV. Adenocarcinomas were correlated with better cancer stage distribution, while small-cell carcinomas (SCLC) were associated with higher stage distribution (p=0.064). False positive rate after positive screening was 59.04% (62/105) and the overall false positive rate of the fourth round was 1.15% (62/5383). Relative to the results of the first three rounds, the LC detection rate was lower (0.80 vs 0.80-1.1) and LC was detected at a more advanced stage (23.8% vs 8.1%). In the fourth round more squamous-cell carcinomas (21.7% vs. 16.3%), SCLC (6.5% vs 3.8%) and bronchioloalveolar carcinomas (8.7% vs 5.3%) were detected. No large-cell carcinomas, large-cell neuroendocrine carcinomas or carcinoids were found in the fourth round. Screening results of the first three rounds led to formation of subgroups with significantly different probability of screening result in the fourth round: participants with previous exclusively negative results had a probability of 97.2% of negative screen compared to participants with ≥1 indeterminate or positive screen (94.6% and 87.1%) in the first three rounds. The risk of detecting LC in the fourth round also differed between these subgroups: exclusively negative results (<1.0%) and any time ≥1 indeterminate or positive result (1.5-1.7%).

      Conclusion:
      The LC detection rate after the third screening round was slightly lower and the stage distribution of screen-detected lung cancers in the fourth round was slightly less favorable. However, the differences seem limited.

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