NK Cell Activity in Smokers Screened for Lung Cancer

Inclusion Criteria: * At the time of registration, subjects must have a current or previous cumulative cigarette smoking history of ≥ 20 pack years (packs per day multiplied by the number of years smoked). If smoking history is between 20 and 29 pack years, subjects must have an additional risk factor (i.e. radon exposure, occupational exposure, personal history of smoking-associated cancer, family history of lung cancer in first-degree relatives, COPD or pulmonary fibrosis). * At the time of registration former smokers without additional risk factor(s) must have quit smoking within the preceding 15 years. * Subjects must be willing to provide blood samples as biospecimens for the study. * At the time of registration, subjects must have recovered from the toxic effects of prior therapy: ≥6 months (182 days) from the last dose of prior cytotoxic therapy. * At the time of registration, subjects must have recovered from the effects of prior pneumonia or acute respiratory infection treated by antibiotics by a physician: ≥12 weeks (84 days) from the first dose of antibiotics. Exclusion Criteria: * Medical or psychiatric condition precluding informed medical consent. * Prior history of lung cancer. * Treatment for or advisement by a physician of evidence of any cancer within the past five years, with the exceptions of non-melanoma skin cancer and most in-situ carcinomas. (Treatment for, or evidence of, melanoma or in-situ bladder/transition cell carcinomas within the preceding five years renders the potential participant ineligible.)