title: Asthma and lung cancer, after accounting for co-occurring respiratory diseases and allergic conditions: a systematic review protocol.
abstract: Asthma is one of the most frequently diagnosed respiratory diseases in the UK, and commonly co-occurs with other respiratory and allergic diseases, such as chronic obstructive pulmonary disease (COPD) and atopic dermatitis. Previous studies have shown an increased risk of lung cancer related to asthma, but the evidence is mixed when accounting for co-occurring respiratory diseases and allergic conditions. A systematic review of published data that investigate the relationship between asthma and lung cancer, accounting for co-occurring respiratory and allergic diseases, will be conducted to investigate the independent association of asthma with lung cancer.
  
  
  
  A systematic review will be conducted, and include original reports of cohort, cross-sectional and case-control studies of the association of asthma with lung cancer after accounting for co-occurring respiratory diseases. Articles published up to June 2016 will be included, and their selection will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A standardised data extraction form will be developed and pretested, and descriptive analyses will be used to summarise the available literature. If appropriate, pooled effect estimates of the association between asthma and lung cancer, given adjustment for a specific co-occurring condition will be estimated using random effects models. Potential sources of heterogeneity and between study heterogeneity will also be investigated.
  
  
  
  The study will be a review of published data and does not require ethical approval. Results will be disseminated through a peer-reviewed publication.
  
  
  
  International Prospective Register for Systematic Reviews (PROSPERO) number CRD42016043341.
authors.affiliation: Department of Non-Communicable Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Denholm
authors.affiliation: Department of Non-Communicable Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Crellin
authors.affiliation: Faculty of Medicine, National Heart & Lung Institute, Imperial College London, London, UK.
authors.forename: Ashwini
authors.initials: A
authors.lastname: Arvind
authors.affiliation: Faculty of Medicine, National Heart & Lung Institute, Imperial College London, London, UK.
authors.forename: Jennifer
authors.identifier: 0000-0003-0149-4869
authors.initials: J
authors.lastname: Quint
mesh_terms: D001249:Asthma / Q000453:epidemiology*; D016022:Case-Control Studies; D015897:Comorbidity; D003430:Cross-Sectional Studies; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology*; D008175:Lung Neoplasms / Q000453:epidemiology*; D012107:Research Design; D012120:Respiration Disorders / Q000453:epidemiology; D000078202:Systematic Reviews as Topic
keywords: Lung cancer; Systematic Review