A large cohort study in Norway showed 38% of subjects had positive mutations of KRAS in non-small cell lung cancer patients, while in Chen’s study involving a lower number of subjects KRAS mutations accounted for 11% of all mutations with a higher prevalence among smokers (20–30%) compared with those who never smoked (7–13%).57 This is in contrast this to study which found no KRAS mutations in subjects diagnosed with lung cancer. Here, KRAS is linked to non-small cell lung carcinoma.