The study consists of recruiting a target population by sending a letter from the Regional Center for Cancer Screening in Ile de France.

In the screening program, a battery of examinations will be carried out at inclusion, one year, 2 years, 3 years, 4 years and 5 years.

The patients will be recruited by correspondence by by sending a letter from the Regional Center for Cancer Screening in Ile de France.

When the patient has agreed to participate, a screening program will be carried out The screening program includes performing a low-dose chest CT scan (STBD), spirometry, blood sampling (biobank + screening for cardiovascular risk factors) on inclusion, at 1 year and at 2 years. Subsequently, a telephone interview will be scheduled for 3 years to collect medical information, for a total follow-up period of 5 years. At each visit, a structured offer of smoking cessation will be proposed and a collection of the quality of life will be carried out. Each year, a telephone call from participants will be scheduled in order to maximize participation

Inclusion Criteria:

• Women and men
• Age: 55 to 74 years old
• Smokers at more than 20 pack-years weaned for less than 15 years
• Affiliated to a social security organization

Exclusion Criteria:

• Presence of signs of PBC
• Subjects with a personal history of PBC of less than 5 years or under treatment
• Presence of serious comorbidities involving the vital prognosis at 6 months
• Subjects who have already benefited from a chest CT scan less than one year old.
• Refusal to participate in the study
• Absence of exposure to tobacco or insufficient exposure to tobacco or withdrawal > 15 years
• Patient on long-term oxygen therapy
• Metal implants (thorax, spine) which can cause a deterioration in the quality of the image of the low dose scanner
• Subject included in another study protocol

Subjects aged 55 to 74, smokers with more than 20 active pack-years or weaned for less than 15 years.