Clinical Research Directory

Inclusion Criteria: 1. Never smokers or have smoked less than 10 pack-years and quitted smoking over 15 years. 2. age from 55 to 75 years for subjects without lung cancer family history; age 50-75 years for subjects with lung cancer family history (age less than 50 but older than the age at diagnosis of the youngest lung cancer proband is also eligible) 3. Having at least one of the following conditions: (1)with family history of lung cancer within 1st, 2nd or 3rd degree relatives (2)with exposure history of environmental tobacco smoke in workplace or in home (3)history of chronic lung disease (Tuberculosis or COPD) (4)the cooking index equal or over than 110 \[cooking index = 2/7 x (days of cooking by pan frying, stir frying, or deep frying in one week) x (cooking years)\] (5)cooking without using cooking ventilation Exclusion Criteria: 1. with history of lung cancer, or with cancers except skin cancer or cervical carcinoma in situ in the past 5 years 2. can not accept invasive diagnostic procedure or surgery 3. have been examined by chest computed tomography in the past 18 months 4. have unexplained hemoptysis in one month 5. weight loss over than 6 kg with unexplained reason among one year 6. pregnant