title: Clinical and dosimetric predictors of radiation pneumonitis in a large series of patients treated with stereotactic body radiation therapy to the lung.
abstract: OBJECTIVE
  To report clinical and dosimetric factors predictive of radiation pneumonitis (RP) in patients receiving lung stereotactic body radiation therapy (SBRT) from a series of 240 patients.
  
  
  METHODS
  Of the 297 isocenters treating 263 patients, 240 patients (n=263 isocenters) had evaluable information regarding RP. Age, gender, current smoking status and pack-years, O2 use, Charlson Comorbidity Index, prior lung radiation therapy (yes/no), dose/fractionation, V5, V13, V20, Vprescription, mean lung dose, planning target volume (PTV), total lung volume, and PTV/lung volume ratio were recorded.
  
  
  RESULTS
  Twenty-nine patients (11.0%) developed symptomatic pneumonitis (26 grade 2, 3 grade 3). The mean V20 was 6.5% (range, 0.4%-20.2%), and the average mean lung dose was 5.03 Gy (0.547-12.2 Gy). In univariable analysis female gender (P=.0257) and Charlson Comorbidity index (P=.0366) were significantly predictive of RP. Among dosimetric parameters, V5 (P=.0186), V13 (P=.0438), and Vprescription (where dose=60 Gy) (P=.0128) were significant. There was only a trend toward significance for V20 (P=.0610). Planning target volume/normal lung volume ratio was highly significant (P=.0024). In multivariable analysis the clinical factors of female gender, pack-years smoking, and larger gross internal tumor volume and PTV were predictive (P=.0094, .0312, .0364, and .052, respectively), but no dosimetric factors were significant.
  
  
  CONCLUSIONS
  Rate of symptomatic RP was 11%. Our mean lung dose was <600 cGy in most cases and V20<10%. In univariable analysis, dosimetric factors were predictive, while tumor size (or tumor/lung volume ratio) played a role in multivariable and univariable and analysis, respectively.
authors.affiliation: University of South Florida School of Medicine, Department of Biostatistics, Moffitt Cancer Center, Tampa, Florida 33612, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Baker
authors.forename: Gang
authors.initials: G
authors.lastname: Han
authors.forename: Siriporn
authors.initials: S
authors.lastname: Sarangkasiri
authors.forename: MaryLou
authors.initials: M
authors.lastname: DeMarco
authors.forename: Carolyn
authors.initials: C
authors.lastname: Turke
authors.forename: Craig W
authors.initials: CW
authors.lastname: Stevens
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Dilling
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000601:surgery*; D015897:Comorbidity; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008175:Lung Neoplasms / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D017564:Radiation Pneumonitis / Q000209:etiology* / Q000473:pathology; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D012306:Risk; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects; D047368:Tumor Burden