To evaluate the effectiveness of LDCT screening in detecting early-stage lung cancers among smokers who do not have symptoms of lung disease.

Tobacco smoking is the leading preventable cause of death worldwide .Chronic Obstructive Pulmonary Disease (COPD), lung cancer, and cardiovascular disease will be responsible for the majority of deaths in the developed world in the coming decades .

COPD is characterised by chronic airflow limitation caused by a combination of small airway inflammation and parenchymal destruction (emphysema) . Since computed tomography (CT) has been validated as a non-invasive technique capable of identifying areas of lung parenchyma with emphysema , several studies have identified a subgroup of apparently healthy smokers who have emphysema but no airway obstruction Furthermore, this subgroup has the highest risk of developing lung cancer among smokers .It has been proposed that systemic inflammation may play an important pathogenic role in carcinogenesis . We will conducted this cross sectional study between. current and former smokers without airway obstruction participating in a lung cancer screening study: a study group of smokers with emphysema on the CT, and a control group of smokers without emphysema.

Inclusion Criteria:

- Participants have at least 45years old had smoked 10 pack-years or more

Exclusion Criteria:

• Age: less than 45 years. Non smoker Evidence of airway obstruction by Pulmonery Function Test

After taking the informed consent, full history will be taken from all patients participating in the study include smoking history. Detailed clinical examination and routine laboratory investigations will be done.

Low Dose CT chest( reduced the radiation exposure to 1.6 mSv ) will be done . Spirometry spirometry will be performed using standard techniques according to ATS-ERS criteria 2019 .

These individuals will further classified into two groups according to the presence or absence of emphysema on the LDCT, the study group have smokers and former smokers with emphysema on the LDCT but no evidence of airway obstruction, whereas the comparison group current and former smokers without emphysema and without obstruction