Characteristics of lung cancers detected by computer tomography screening in the randomized NELSON trial

The NELSON (Nederlands Leuvens Longkanker Screenings Onderzoek) trial is, with 15,822 participants, the largest European lung cancer computer tomography screening trial. A volumetry-based screening strategy, stringent criteria for a positive screening, and an increasing length of screening interval are particular features of the NELSON trial.To determine the effect of stringent referral criteria and increasing screening interval on the characteristics of screen-detected lung cancers, and to compare this across screening rounds, between sexes, and with other screening trials.All NELSON participants with screen-detected lung cancer in the first three rounds were included. Lung cancer stage at diagnosis, histological subtype, and tumor localization were compared between the screening rounds, the sexes, and with other screening trials.In the first three screening rounds, 200 participants were diagnosed with 209 lung cancers. Of these lung cancers, 70.8\% were diagnosed at stage I and 8.1\% at stage IIIB-IV, and 51.2\% were adenocarcinomas. There was no significant difference in cancer stage, histology, or tumor localization across the screening rounds. Women were diagnosed at a significantly more favorable cancer stage than men. Compared with other trials, the screen-detected lung cancers of the NELSON trial were relatively more often diagnosed at stage I and less often at stage IIIB-IV.Despite stringent criteria for a positive screening, an increasing length of screening interval, and few female participants, the screening strategy of the NELSON trial resulted in a favorable cancer stage distribution at diagnosis, which is essential for the effectiveness of our screening strategy. Clinical trial registered with www.trialregister.nl (ISRCTN63545820).