title: Analysis of biologically equivalent dose of stereotactic body radiotherapy for primary and metastatic lung tumors.
abstract: OBJECTIVE
  The purpose of this study was to determine the optimal biologically equivalent dose (BED) for stereotactic body radiotherapy (SBRT) by comparing local control rates in proportion to various total doses and fractionation schedules.
  
  
  METHODS
  Thirty-four patients with early non-small-cell lung cancer and a single metastatic lung tumor were included in this study. Differences in local control rates were evaluated according to gender, primary tumor site, response, tumor size, and BED. For comparison of BEDs, the prescribed dose for SBRT was stratified according to three groups: high (BED > 146 Gy), medium to high (BED, 106 to 146 Gy), and low to medium (BED < 106 Gy).
  
  
  RESULTS
  For all patients, the overall local control rate was 85.3% at two years after treatment. Five local recurrences were observed, and, notably, all of them were observed in the low to medium BED group. Significantly higher local control rates were observed for patients with a complete response than for those with a partial response or stable disease (p < 0.001). Twenty-six patients with a tumor size of < 3 cm showed no dose-response relationship in the low to medium, medium to high, and high BED groups, whereas eight patients with a tumor size of ≥ 3 cm showed a significant dose-response relationship. The observed 2-year local recurrence-free survival rates in patients with a tumor size of < 3 cm and in those with a tumor size of ≥ 3 cm were 96.2% and 50.0%, respectively, which were significantly different (p=0.007).
  
  
  CONCLUSIONS
  BED > 100 Gy is required in order to achieve a > 85% local control rate regardless of tumor size. The optimal dose for small tumors of < 3 cm appears to be within a range below 150 Gy BED. Escalation of BED to high levels (> 150 Gy) may be required for patients with a tumor size larger than 3 cm.
authors.affiliation: Department of Radiation Oncology, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Sungkwang
authors.initials: S
authors.lastname: Park
authors.affiliation: Department of Preventive Medicine, Inje University College of Medicine, Busan, Korea.
authors.forename: Sanghwa
authors.initials: S
authors.lastname: Urm
authors.affiliation: Department of Radiation Oncology, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Heunglae
authors.initials: H
authors.lastname: Cho
keywords: Biologically effective dose; Lung; Neoplasm metastasis; Stereotactic body radiotherapy