title: The relationship between external beam radiotherapy dose and chronic urinary dysfunction--a methodological critique.
abstract: OBJECTIVE
  To perform a methodological critique of the literature evaluating the relationship between external beam radiotherapy dose/volume parameters and chronic urinary dysfunction to determine why consistent associations between dose and dysfunction have not been found.
  
  
  METHODS
  The radiotherapy literature was reviewed using various electronic medical search engines with appropriate keywords and MeSH headings. Inclusion criteria comprised of; English language articles, published between 1999 and June 2009, incorporating megavoltage external beam photons in standard-sized daily fraction. A methodological critique was then performed, evaluating the factors affected in the quantification of radiotherapy dose and chronic urinary dysfunction.
  
  
  RESULTS
  Nine of 22 eligible studies successfully identified a clinically and statistically significant relationship between dose and dysfunction. Accurate estimations of external beam radiotherapy dose were compromised by the frequent use of dosimetric variables which are poor surrogates for the dose received by the lower urinary tract tissue and do not incorporate the effect of daily variations in isocentre and bladder position. The precise categorization of chronic urinary dysfunction was obscured by reliance on subjective and aggregated toxicity metrics which vary over time.
  
  
  CONCLUSIONS
  A high-level evidence-base for the relationship between external beam radiotherapy dose and chronic urinary dysfunction does not currently exist. The quantification of the actual external beam dose delivered to the functionally important tissues using dose accumulation strategies and the use of objective measures of individual manifestations of urinary dysfunction will assist in the identification of robust relationships between dose and urinary dysfunction for application in widespread clinical practice.
authors.affiliation: Princess Margaret Hospital and Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada. Tara.Rosewall@rmp.uhn.on.ca
authors.forename: Tara
authors.initials: T
authors.lastname: Rosewall
authors.forename: Charles
authors.initials: C
authors.lastname: Catton
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Currie
authors.forename: Andrew
authors.initials: A
authors.lastname: Bayley
authors.forename: Peter
authors.initials: P
authors.lastname: Chung
authors.forename: Janelle
authors.initials: J
authors.lastname: Wheat
authors.forename: Michael
authors.initials: M
authors.lastname: Milosevic
mesh_terms: D002908:Chronic Disease; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries; D011878:Radiotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D014551:Urinary Tract / Q000528:radiation effects*; D014570:Urologic Diseases / Q000209:etiology*