Norway Comprehensive details of cases and controls have been previously published.24 Briefly, a systematic series of 426 patients with histologically proven non-small cell LC treated with surgery were ascertained through university hospitals in Oslo or Bergen between 1986 and 2001. All of the cases were either smokers at the time of surgery or ex-smokers. Healthy controls were recruited from a general health survey of individuals conducted by the National Health Surveys in the Oslo area (HUBRO) between 2000 and 2001, or in western Norway. Among them, smokers without any known history of cancer were randomly selected and frequency matched to the cases on age, smoking dose (pack-years) and gender. Cases and controls were interviewed using questionnaires that allowed collection of the same demographic and lifestyle information. Both cases and controls were Norwegians of European descent. The study was approved by the regional ethical committee in accordance with the Helsinki Declaration.
