title: Do dose-volume metrics predict pulmonary function changes in lung irradiation?
abstract: OBJECTIVE
  To examine the ability of standard dose-volume metrics to predict pulmonary function changes as measured by pulmonary function tests (PFTs) in a group of patients with non-small-cell lung cancer treated with nonconventional beam arrangements on a Phase I dose-escalation study. In addition, we wanted to examine the correlation between these metrics.
  
  
  METHODS
  Forty-three patients received a median treatment dose of 76.9 Gy (range 63-102.9). Eight patients also received induction chemotherapy with cisplatin and vinorelbine. They all had pre- and posttreatment PFTs >/=3 months (median 6.2) after treatment. The volume of normal lung treated to >20 Gy, effective volume, and mean lung dose were calculated for both lungs for all patients. Linear regression analysis was performed to determine whether correlations existed between the metrics and changes in the PFTs. Additionally, the three metrics were compared with each other to assess the degree of intermetric correlation.
  
  
  RESULTS
  No correlation was found between the volume of normal lung treated to >20 Gy, effective volume, and mean lung dose and changes in the PFTs. Subgroup analyses of patients without atelectasis before irradiation, Stage I and II disease, or treatment without induction chemotherapy were also performed. Again, no correlation was found between the dose-volume metrics and the PFT changes. The intermetric correlation was good among all three dose-volume metrics.
  
  
  CONCLUSIONS
  In this relatively small series of patients, dose-volume metrics that correlate with the risk of pneumonitis did not provide a good model to predict early changes in pulmonary function as measured with PFTs.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA. Aamallen@umich.edu
authors.forename: A M
authors.initials: AM
authors.lastname: Allen
authors.forename: G T
authors.initials: GT
authors.lastname: Henning
authors.forename: R K
authors.initials: RK
authors.lastname: Ten Haken
authors.forename: J A
authors.initials: JA
authors.lastname: Hayman
authors.forename: M K
authors.initials: MK
authors.lastname: Martel
mesh_terms: D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D017564:Radiation Pneumonitis / Q000503:physiopathology; D011874:Radiometry; D020266:Radiotherapy, Conformal; D012044:Regression Analysis; D012129:Respiratory Function Tests