title: Influence of connective tissue diseases on the expression of radiation side effects: a systematic review.
abstract: OBJECTIVE
  Patient related co-factors may increase the risk of radiation morbidity. Connective tissue diseases (CTD) are among the co-morbidities that are relatively well studied and have been shown to be of potential clinical relevance for radiotherapy. The aim of this systematic review is to quantify the contribution of CTD to the risk of radiation related side effects.
  
  
  METHODS
  Relevant publications reporting the outcome of radiotherapy in patients with CTD were retrieved according to a standardized query and evaluated for their methodology and quality of reporting, using defined quality criteria. A quantitative estimate of the relative risk of developing side effects in patients with CTD was derived from the observed proportions of responders in patients with or without CTD. Risk estimates were synthesized across studies.
  
  
  RESULTS
  Eight studies which include data of 9-209 patients who had CTD and were treated with radiotherapy were identified and reviewed. Three of these studies included data suited for further quantitative analysis. The test of the uni-directional hypothesis that patients with CTD had an increased risk of late effects after radiotherapy reached statistical significance, the one-tailed P-value being 0.03. The pooled relative risk was 2.0 with 95% confidence interval (0.99, 4.1).
  
  
  CONCLUSIONS
  CTD is associated with an increased risk of late radiation induced normal tissue reaction. The literature published to date provides some support for this assertion although most of the reports are plagued by methodological weaknesses, thus calling for a large coordinated study.
authors.affiliation: Department of Radiotherapy and Radiation Oncology, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Hölscher
authors.forename: Søren M
authors.initials: SM
authors.lastname: Bentzen
authors.forename: Michael
authors.initials: M
authors.lastname: Baumann
mesh_terms: D003240:Connective Tissue Diseases / Q000503:physiopathology*; D006801:Humans; D011830:Radiation Effects; D011832:Radiation Injuries / Q000209:etiology; D011878:Radiotherapy / Q000009:adverse effects*; D012306:Risk