Frequency of incidental diagnosis in contemporary lung cancer care

<bold>Introduction:</bold> Lung cancer (LC) is usually discovered at an advanced stage due to the low symptom burden in the early stages. An incidental diagnosis may occur when patients are investigated for non-related symptoms of other diseases. <bold>Objective:</bold> To assess the occurrence of incidental diagnosis of LC preceding the start of LC screening. <bold>Methods:</bold> This real-world observational study included 523 patients with LC from all 4 hospitals in Frisia, a province of the Netherlands, diagnosed in 2021. The available data from the National Cancer Registry was supplemented with information from medical files. Patients were classified as incidental depending on the absence of LC-related symptoms at diagnosis. <bold>Results:</bold> Incidental diagnosis was noted in 28.5% of patients, rising to 84.6% of patients with stage I disease, and was uncommon in younger patients (<italic>p</italic>=.003) and more common in ex-smokers (<italic>p</italic>=.004). The mode of detection and motives for imaging were highly variable. 73.2% of incidental diagnoses were referred by other clinical specialties. Incidental pulmonary nodules were found in 52.3% of incidental diagnoses and were related to the staging or surveillance of other malignancies in 27 out of 78 cases. Only 35.2% of patients with incidental diagnoses would have been eligible for participation in a screening program. The 2-year survival rates were 65.7% (95% CI 57.5-72.7) and 22.2% (95% CI 18.1-26.3) for incidental and symptomatic diagnoses, respectively. Survival rates did not differ for patients with stage I disease (<italic>p</italic>=.87). <bold>Conclusion:</bold> Incidental diagnosis of LC is very frequent. Most incidental diagnoses were made in patients ineligible for a screening program.