P M Marcus1, P C Prorok. 1. Division of Cancer Prevention, National Cancer Institute, Bethesda, MD 20892-7354, USA.
Abstract
OBJECTIVES: To examine whether age at entry, history of cigarette smoking, exposure to non-tobacco lung carcinogens, or previous pulmonary illnesses were confounders or effect modifiers of the relation between screening and lung cancer mortality in the Mayo Lung Project. SETTING: The Mayo Lung Project was a randomised, controlled, clinical trial conducted between 1971 and 1986 in 9211 male smokers over the age of 45 in Minnesota (USA). The group screened received chest x ray examination and sputum cytology every four months for six years. The unscreened group were recommended to obtain usual care (annual chest x ray examination and sputum cytology). After follow up, lung cancer mortality was similar in both groups. METHODS: Proportional hazard models were used to analyse data. A variable was considered a confounder if its inclusion in a model changed the rate ratio for screening by more than 15%; a variable was considered an effect modifier if its stratum-specific rate ratio for screening differed by a factor of two. RESULTS: None of the four aforementioned variables changed the rate ratio associated with screening (1.07) by more than 2%. The effect of screening may have differed by years smoked (rate ratio for smoking fewer than 30 years 2.4; rate ratio for smoking 30 or more years 1.0), though we suspect that this result occurred by chance. CONCLUSION: Adjustment for or stratification by four established lung cancer risk factors did not alter the original findings of the Mayo Lung Project.
RCT Entities:
OBJECTIVES: To examine whether age at entry, history of cigarette smoking, exposure to non-tobaccolung carcinogens, or previous pulmonary illnesses were confounders or effect modifiers of the relation between screening and lung cancer mortality in the Mayo Lung Project. SETTING: The Mayo Lung Project was a randomised, controlled, clinical trial conducted between 1971 and 1986 in 9211 male smokers over the age of 45 in Minnesota (USA). The group screened received chest x ray examination and sputum cytology every four months for six years. The unscreened group were recommended to obtain usual care (annual chest x ray examination and sputum cytology). After follow up, lung cancer mortality was similar in both groups. METHODS: Proportional hazard models were used to analyse data. A variable was considered a confounder if its inclusion in a model changed the rate ratio for screening by more than 15%; a variable was considered an effect modifier if its stratum-specific rate ratio for screening differed by a factor of two. RESULTS: None of the four aforementioned variables changed the rate ratio associated with screening (1.07) by more than 2%. The effect of screening may have differed by years smoked (rate ratio for smoking fewer than 30 years 2.4; rate ratio for smoking 30 or more years 1.0), though we suspect that this result occurred by chance. CONCLUSION: Adjustment for or stratification by four established lung cancer risk factors did not alter the original findings of the Mayo Lung Project.
Authors: Renée Manser; Anne Lethaby; Louis B Irving; Christine Stone; Graham Byrnes; Michael J Abramson; Don Campbell Journal: Cochrane Database Syst Rev Date: 2013-06-21
Authors: Huiqin Yang; Jo Varley-Campbell; Helen Coelho; Linda Long; Sophie Robinson; Tristan Snowsill; Ed Griffin; Jaime Peters; Chris Hyde Journal: Diagn Progn Res Date: 2019-11-28