title: Predicting risk factors for radiation pneumonitis after stereotactic body radiation therapy for primary or metastatic lung tumours.
abstract: OBJECTIVE
  To investigate risk factors for radiation-induced pneumonitis (RP) after hypofractionated stereotactic body radiotherapy (SBRT) in patients with lung tumours.
  
  
  METHODS
  From May 2004 to January 2016, 66 patients with 71 primary or metastatic lung tumours were treated with SBRT; these 71 cases were retrospectively analyzed for RP. To explore the risk factors for RP, the following factors were investigated: age, sex, performance status, operability, number of treatments, respiratory gating, pulmonary emphysema, tumour location and subclinical interstitial lung disease (ILD). Irradiated underlying lung volumes of more than 5 Gy, 10 Gy, 20 Gy and 30 Gy (Lung V5, V10, V20and V30), mean lung dose and volumes of gross tumour volume (in cubic centimetre) and planning target volume were calculated for possible risk factors of RP.
  
  
  RESULTS
  The median follow-up period was 32 months. RP of Grade 2 or more, according to the Common Terminology Criteria for Adverse Events v. 4.0, was detected in 6 (8.4%) of the 71 cases. Grade 5 RP was identified in two cases. Of the risk factors of RP, subclinical ILD was the only factor significantly associated with the occurrence of RP of Grade 2 or more (p < 0.001). Both cases with Grade 5 RP had ILD with a honeycombing image.
  
  
  CONCLUSIONS
  Subclinical ILD was the only significant factor for Grade 2-5 RP. In addition, the cases with honeycombing had a high potential for fatality related to severe RP. Patients with subclinical ILD should be carefully monitored for the occurrence of severe RP after SBRT. Advances in knowledge: Hypofractionated SBRT for primary or metastatic lung tumours provides a high local control rate and safe treatment.
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Okubo
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Itonaga
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Saito
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Sachika
authors.initials: S
authors.lastname: Shiraishi
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Mikami
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Hidetugu
authors.initials: H
authors.lastname: Nakayama
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Sakurada
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Sugahara
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Koizumi
authors.affiliation: Department of Radiology, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Tokuuye
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005544:Forecasting; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy* / Q000556:secondary*; D008297:Male; D008875:Middle Aged; D017564:Radiation Pneumonitis / Q000453:epidemiology* / Q000209:etiology*; D016634:Radiosurgery / Q000009:adverse effects*; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors