The main objective of the study is to measure adherence to a lung cancer screening program using low-dose thoracic CT.

Secondary objectives

1. To evaluate patient compliance over the entire duration of the screening program
2. To assess patient smoking cessation
3. To describe radiation doses received during CT scans
4. To identify organizational constraints for general practitioners
5. To compare stages at diagnosis before and after implementation of screening program

Conduct of research Eligible patients will be identified by general practitioners. Patients included will require a low-dose thoracic CT scan to be performed by a radiologist of their choice. Smoking cessation will be systematically proposed, and will be carried out by the general practitioner or a tobaccologist.

The radiation dose from thoracic CT scans should not exceed 100 mGy.cm Product Dose Length (i.e. < 1.5 mSv). Imaging reports will be forwarded to the general practitioner.

If the first CT scan is negative (T0): a second scan will be scheduled 1 year later (T1). If this second scan is also negative, in the absence of lung cancer risk factors other than smoking, scans will then be performed every two years. In the presence of a risk factor for lung cancer (other than tobacco), screening will remain annual.

In the event of a result classified as uncertain: a follow-up scan is scheduled at 3 months ; if the follow-up scan is negative, the next screening will be scheduled 1 year after this follow-up scan. If the screening performed 1 year later is also negative, subsequent screenings will be performed annually.

In the event of a positive result: the general practitioner will refer the patient to a pneumologist of his/her choice for further examinations; data from these additional examinations will be collected.

The screening protocol may evolve in line with recommendations issued by the French National Authority for Health (HAS).

For participants undergoing CT scan at the imaging department of Emile Muller hospital in Mulhouse (GHRMSA), a blood sample will be collected (optional) for subsequent biomarker assays.

Inclusion Criteria:

• Patients aged 50 to 74 years
• Smoking OR having smoked (withdrawal of <15 years): ≥15 cigarettes/day for ≥25 years OR ≥10 cigarettes/day for ≥30 years
• Affiliated or beneficiary of a social security scheme
• Written informed consent

Exclusion Criteria:

• Inability to walk up two flights of stairs without stopping
• BMI > 35 kg/m²
• Recent chest CT scan < 1 year
• Personal history of lung cancer < 5 years or under treatment
• Personal history of cancer being monitored by chest CT scan
• Contraindication to lung cancer treatment or diagnostic investigations
• Current or recent respiratory symptoms immediately suggestive of lung cancer
• Pregnant or breast-feeding woman
• Person under court protection, guardianship or curatorship
• Person deprived of liberty by judicial or administrative decision.