Inclusion Criteria:  Subjects aged 50-80 years at time of consent Increased risk of lung cancer defined by: at least 20 pack-year smoking history and currently smoke or have quit within the past 15 years Willing to consent to the investigational blood draw during index LDCT screening visit and before any invasive procedures or treatment for lung cancer diagnosis Willing to consent to a 1-year, 2-year and additional follow-up per protocol  Exclusion Criteria:  Subject has not smoked for 15 or more years Subject has a health problem that substantially limits life expectancy and/or the ability or willingness to have curative lung surgery Subjects undergoing diagnostic low-dose CT scan for investigation of symptoms Preexisting or history of lung cancer Previously diagnosed high-risk lung lesion History of any malignancy (subjects who have undergone surgical removal of skin squamous cell cancer may be enrolled provided the procedure was completed at least 12 months prior to the date of provision of informed consent for the study) Currently taking any anti-neoplastic or disease-modifying anti-rheumatic drugs (DMARDs) Currently receiving treatment for pneumonia Any major physical trauma (e.g., disruption of tissue, surgery, organ transplant, blood product transfusion) within the 30 days leading up to the provision of informed consent Known medical condition which, in the opinion of the investigator, should preclude enrollment into the study