title: [The time factor and time-dose-prescription in the radiotherapy of head and neck tumors].
abstract: BACKGROUND
  Clinical data on head and neck tumors presented by Withers et al. are reexamined. Recently it was argued that the relationship between TCD50 and treatment time might be influenced by the practice of prescription.
  
  
  METHODS
  In a computer simulation the impact of treatment outcome on the time factor is investigated. For this the genuine local tumor control rates were replaced by either tumor failure rate or by random numbers.
  
  
  RESULTS
  The time factor is independent from local tumor control rates in all simulations.
  
  
  CONCLUSIONS
  The increase of TCD50 with treatment time reflects solely dose-time prescription habits. The data provide no significant evidence either for an impact of treatment duration or for repopulation during radiotherapy in head and neck tumors.
authors.affiliation: Institut für Biophysik und Strahlenbiologie, Universität Hamburg.
authors.forename: H H
authors.initials: HH
authors.lastname: Dubben
mesh_terms: D003198:Computer Simulation; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D011879:Radiotherapy Dosage; D013997:Time Factors
vernacular_title: Zeitfaktor und Zeit-Dosis-Verschreibung in der Strahlentherapie von Kopf-Hals-Tumoren.