Methods and kits for determining a risk of a subject, or subjects for developing lung cancer is disclosed. The method comprises determining a level of catalytic activity of N-methylpurine DNA glycosylase (MPG), or apurinic/apyrimidinic endonuclease 1 (APE1), or both, or MPG and 8-oxoguanine DNA glycosylase (OGG1), or MPG and APE1 and OGG1 in peripheral blood cells of a subject, wherein levels of MPG above a predetermined reference value, or APE1 or OGG1, or a integrated DNA repair score below a predetermined reference value is indicative of an increased risk of developing lung cancer.