title: Prognostic factors for local control of stage I non-small cell lung cancer in stereotactic radiotherapy: a retrospective analysis.
abstract: BACKGROUND
  The purpose of this study is to investigate the prognostic factors of stereotactic radiotherapy for stage I NSCLC to improve outcomes.
  
  
  METHODS
  Stage I non-small cell lung cancer patients who were treated with stereotactic radiotherapy between 2005 and 2009 at our hospital were enrolled in this study. The primary endpoint was local control rate. Survival estimates were calculated from the completion date of radiotherapy using the Kaplan-Meier method. The prognostic factors including patients' characteristics and dose-volume histogram parameters were evaluated using Cox's proportional hazard regression model.
  
  
  RESULTS
  Eighty patients (81 lesions) treated with 3 dose levels, 48 Gy/4 fractions, 60 Gy/8 fractions and 60 Gy/15 fractions, were enrolled in this study. Median follow-up was 30.4 months (range, 0.3 - 78.5 months). A Cox regression model showed T factor (p = 0.013), biological effective dose calculated from prescribed dose (BED10) (p = 0.048), and minimum dose for PTV (p = 0.013) to be prognostic factors for local control. Three-year overall survival rate and local control rate were 89.9% (T1: 86.8%, T2: 100%) and 89.0% (T1: 97.9%; T2: 64.8%), respectively. When the 3-year local control rates were examined by prescribed doses, they were 100% for the dose per fraction of 48 Gy /4 fractions (105.6 Gy BED10), 82.1% for 60 Gy/8 fractions (105 Gy BED10), and 57.1% for 60 Gy/15 fractions (84 Gy BED10). The median value of the minimum dose for PTV (%) was 89.88 (%), and the 3-year local control rates were 100% in those with the minimum dose for PTV (%) ≥ 89.88% and 79.2% in those with the minimum dose for PTV (%) < 89.88%.
  
  
  CONCLUSIONS
  Our results suggest that T factor, BED10, and minimum dose for PTV influence the local control rate. Local control rate can be improved by securing the minimum dose for PTV.
authors.affiliation: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan. guldoktu@gmail.com
authors.forename: Yuko
authors.initials: Y
authors.lastname: Shirata
authors.forename: Keiichi
authors.initials: K
authors.lastname: Jingu
authors.forename: Masashi
authors.initials: M
authors.lastname: Koto
authors.forename: Masaki
authors.initials: M
authors.lastname: Kubozono
authors.forename: Ken
authors.initials: K
authors.lastname: Takeda
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Sugawara
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kadoya
authors.forename: Haruo
authors.initials: H
authors.lastname: Matsushita
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D016634:Radiosurgery; D012189:Retrospective Studies; D016896:Treatment Outcome