title: Late regional density changes of the lung after radiotherapy for breast cancer.
abstract: OBJECTIVE
  To investigate density changes in lung tissue, 3-4 years after postoperative adjuvant radiotherapy for breast cancer, based on dose dependence and regional differences.
  
  
  METHODS
  Sixty-one breast cancer patients, who had received computed tomography (CT) based postoperative radiotherapy, were included. CT scans were performed 35-51 months after start of radiotherapy. Dose information and CT scans from before and after radiotherapy were geometrically aligned in order to analyse changes in air-filled fraction (derived from CT density) as a function of dose for different regions of the lung.
  
  
  RESULTS
  Dose-dependent reduction of the air-filled fraction was shown to vary between the different regions of the lung. For lung tissue receiving about 50 Gy, the largest reduction in air-filled fraction was found in the cranial part of the lung. An increased air-filled fraction was observed for lung tissue irradiated to doses below 20 Gy, indicating compensatory response.
  
  
  CONCLUSIONS
  The treatment-induced change in whole-lung density is a weighted response, involving the different regions, the irradiated volumes, and dose levels to these volumes. Simplistic models may therefore not be appropriate for describing the whole-lung dose-volume-response relationship following inhomogeneous irradiation.
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Rikshospitalet University Hospital, Oslo, Norway.
authors.forename: Randi
authors.initials: R
authors.lastname: Vågane
authors.forename: Turi
authors.initials: T
authors.lastname: Danielsen
authors.forename: Sophie Dorothea
authors.initials: SD
authors.lastname: Fosså
authors.forename: Erik
authors.initials: E
authors.lastname: Løkkevik
authors.forename: Dag Rune
authors.initials: DR
authors.lastname: Olsen
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D017024:Chemotherapy, Adjuvant; D003131:Combined Modality Therapy; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008168:Lung / Q000473:pathology / Q000528:radiation effects*; D008875:Middle Aged; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant; D011795:Surveys and Questionnaires; D014057:Tomography, X-Ray Computed