title: Lung Size and the Risk of Radiation Pneumonitis.
abstract: OBJECTIVE
  The purpose of this study was to identify patient populations treated for non-small cell lung cancer (NSCLC) who may be more at risk of radiation pneumonitis.
  
  
  METHODS
  A total of 579 patients receiving fractionated 3D conformal or intensity modulated radiation therapy (IMRT) for NSCLC were included in the study. Statistical analysis was performed to search for cohorts of patients with higher incidences of radiation pneumonitis. In addition to conventional risk factors, total and spared lung volumes were analyzed. The Lyman-Kutcher-Burman (LKB) and cure models were then used to fit the incidence of radiation pneumonitis as a function of lung dose and other factors.
  
  
  RESULTS
  Total lung volumes with a sparing of less than 1854 cc at 40 Gy were associated with a significantly higher incidence of radiation pneumonitis at 6 months (38% vs 12% for patients with larger volumes, P<.001). This patient cohort was overwhelmingly female and represented 22% of the total female population of patients and nearly 30% of the cases of radiation pneumonitis. An LKB fit to normal tissue complication probability (NTCP) including volume as a dose modifying factor resulted in a dose that results in a 50% probability of complication for the smaller spared volume cohort that was 9 Gy lower than the fit to all mean lung dose data and improved the ability to predict radiation pneumonitis (P<.001). Using an effective dose parameter of n=0.42 instead of mean lung dose further improved the LKB fit. Fits to the data using the cure model produced similar results.
  
  
  CONCLUSIONS
  Spared lung volume should be considered when treating NSCLC patients. Separate dose constraints based on smaller spared lung volume should be considered. Smaller spared lung volume patients should be followed closely for signs of radiation pneumonitis.
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: tmbriere@mdanderson.org.
authors.forename: Tina Marie
authors.initials: TM
authors.lastname: Briere
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Shane
authors.initials: S
authors.lastname: Krafft
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Liao
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Mary K
authors.initials: MK
authors.lastname: Martel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D015994:Incidence; D008168:Lung / Q000033:anatomy & histology* / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D011336:Probability; D017564:Radiation Pneumonitis / Q000453:epidemiology / Q000209:etiology*; D020266:Radiotherapy, Conformal / Q000009:adverse effects; D018570:Risk Assessment; D012737:Sex Factors; D013997:Time Factors; D047368:Tumor Burden