title: Dosimetric selection for helical tomotherapy based stereotactic ablative radiotherapy for early-stage non-small cell lung cancer or lung metastases.
abstract: BACKGROUND
  No selection criteria for helical tomotherapy (HT) based stereotactic ablative radiotherapy (SABR) to treat early stage non-small cell lung cancer (NSCLC) or solitary lung metastases has been established. In this study, we investigate the dosimetric selection criteria for HT based SABR delivering 70 Gy in 10 fractions to avoid severe toxicity in the treatment of centrally located lesions when adequate target dose coverage is desired.
  
  
  METHODS
  78 HT-SABR plans for solitary lung lesions were created to prescribe 70 Gy in 10 fractions to the planning target volume (PTV). The PTV was set to have ≥95% PTV receiving 70 Gy in each case. The cases for which dose constraints for ≥1 OAR could not be met without compromising the target dose coverage were compared with cases for which all target and OAR dose constraints were met.
  
  
  RESULTS
  There were 23 central lesions for which OAR dose constraints could not be met without compromising PTV dose coverage. Comparing to cases for which optimal HT-based SABR plans were generated, they were associated with larger tumor size (5.72±1.96 cm vs. 3.74±1.49 cm, p<0.0001), higher lung dose, increased number of immediately adjacent OARs ( 3.45±1.34 vs. 1.66±0.81, p<0.0001), and shorter distance to the closest OARs (GTV: 0.26±0.22 cm vs. 0.88±0.54 cm, p<0.0001; PTV 0.19±0.18 cm vs. 0.48±0.36 cm, p = 0.0001).
  
  
  CONCLUSIONS
  Delivery of 70 Gy in 10 fractions with HT to meet all the given OAR and PTV dose constraints are most likely when the following parameters are met: lung lesions ≤3.78 cm (11.98 cc), ≤2 immediately adjacent OARs which are ≥0.45 cm from the gross lesion and ≥0.21 cm from the PTV.
authors.affiliation: Department of Radiation Oncology, West Virginia University, Morgantown, West Virginia, United States of America. achiaz2010@gmail.com
authors.forename: Alexander
authors.initials: A
authors.lastname: Chi
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Liao
authors.forename: Nam P
authors.initials: NP
authors.lastname: Nguyen
authors.forename: Jiahong
authors.initials: J
authors.lastname: Xu
authors.forename: James S
authors.initials: JS
authors.lastname: Welsh
authors.forename: Si Young
authors.initials: SY
authors.lastname: Jang
authors.forename: Carol
authors.initials: C
authors.lastname: Howe
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008168:Lung / Q000473:pathology / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D036542:Tomography, Spiral Computed