title: An improved model for predicting radiation pneumonitis incorporating clinical and dosimetric variables.
abstract: OBJECTIVE
  Single dose-volume metrics are of limited value for the prediction of radiation pneumonitis (RP) in day-to-day clinical practice. We investigated whether multiparametric models that incorporate clinical and physiologic factors might have improved accuracy.
  
  
  METHODS
  The records of 160 patients who received radiation therapy for non-small-cell lung cancer were reviewed. All patients were treated to the same dose and with an identical technique. Dosimetric, pulmonary function, and clinical parameters were analyzed to determine their ability to predict for the subsequent development of RP.
  
  
  RESULTS
  Twenty-seven patients (17%) developed RP. On univariate analysis, the following factors were significantly correlated with the risk of pneumonitis: fractional volume of lung receiving >5-20 Gy, absolute volume of lung spared from receiving >5-15 Gy, mean lung dose, craniocaudal position of the isocenter, transfer coefficient for carbon monoxide (KCOc), total lung capacity, coadministration of angiotensin converting enzyme inhibitors, and coadministration of angiotensin receptor antagonists. By combining the absolute volume of lung spared from receiving >5 Gy with the KCOc, we defined a new parameter termed Transfer Factor Spared from receiving >5 Gy (TFS(5)). The area under the receiver operator characteristic curve for TFS(5) was 0.778, increasing to 0.846 if patients receiving modulators of the renin-angiotensin system were excluded from the analysis. Patients with a TFS(5) <2.17 mmol/min/kPa had a risk of RP of 30% compared with 5% for the group with a TFS(5) ≥ 2.17.
  
  
  CONCLUSIONS
  TFS(5) represents a simple parameter that can be used in routine clinical practice to more accurately segregate patients into high- and low-risk groups for developing RP.
authors.affiliation: Gloucestershire Oncology Centre, Cheltenham General Hospital, Cheltenham, UK. peter.jenkins@glos.nhs.uk
authors.forename: Peter
authors.initials: P
authors.lastname: Jenkins
authors.forename: Joanne
authors.initials: J
authors.lastname: Watts
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D057911:Angiotensin Receptor Antagonists / Q000008:administration & dosage; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000008:administration & dosage; D019540:Area Under Curve; D002248:Carbon Monoxide / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning; D012372:ROC Curve; D017564:Radiation Pneumonitis / Q000209:etiology*; D011879:Radiotherapy Dosage; D012084:Renin-Angiotensin System; D018570:Risk Assessment / Q000379:methods; D014109:Total Lung Capacity
chemical_list: D057911:Angiotensin Receptor Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors; D002248:Carbon Monoxide