Abstract: The invention provides a method for detection of lung cancer, or predisposition to lung cancer, in a subject that comprises assaying a test sample of peripheral blood from the subject for a marker of DNA damage. An elevated amount of marker present in the test sample compared to control sample is indicative of lung cancer, or predisposition to lung cancer. The method can be adapted for quantitatively monitoring the efficacy of treatment of lung cancer in a subject. Markers of DNA damage include single- and/or double-stranded breaks in leukocytes, oxidative DNA damage in leukocytes, or a marker of nitrotyrosine oxidative activity (protein nitrosylation in leukocytes). This unexpected discovery of markers of systemic genotoxicity that can be tested using circulating leukocytes enables detection of lung cancer, or predisposition to lung cancer, with a relatively simple and minimally invasive assay using peripheral blood.