Clinical urgency of incidental findings in the first year of the 4-IN-THE-LUNG-RUN lung cancer screening program

Introduction Low-dose CT lung cancer screening (LCS) inevitably detects incidental findings (IFs) beyond its primary purpose; while some offer clinical benefit, they also risk overdiagnosis, overtreatment, and increased healthcare costs. This study evaluated the clinical urgency of IFs during the first year of the 4-IN-THE-LUNG-RUN LCS program. Methods Participants in the Dutch arm of the 4-IN-THE-LUNG-RUN program who underwent baseline and annual CT screening between December-2022 and May-2025 were included. Clinical urgency was assessed by the proportion of radiologist-described IFs that, following centralized expert adjudication, were reported to primary care, referred for further work-up, or required (urgent) referral or intervention. At annual screening, all previously reported IFs were classified as new, stable, progressing, or surgically intervened. Results Among 4122 participants (56.5% male, median age 68 years), IFs were described in 291 participants (7.1%) across both screening rounds. Following centralized adjudication, 75 participants (1.8%) had an IF reported to primary care, of whom 19 (0.5%) were referred for further work-up. At baseline, 67 IFs in 58 participants (1.4%) were reported to primary care, with 10 referred for clinical work-up, including one urgent referral. Four received surgical intervention, two cardiovascular IFs were non-symptomatic and thus screening-driven. At annual screening, the remaining baseline IFs were predominantly stable (59/63), only four showed progression and were subsequently re-reported. New IFs at annual screening were rare. Conclusion While lung cancer screening inevitably reveals findings beyond lung cancer, the majority are not clinically relevant, rarely require urgent intervention, and can be effectively managed within the screening program.