title: Simultaneous integrated protection : A new concept for high-precision radiation therapy.
abstract: OBJECTIVE
  Stereotactic radiotherapy near serial organs at risk (OAR) requires special caution. A novel intensity-modulated radiotherapy (IMRT) prescription concept termed simultaneous integrated protection (SIP) for quantifiable and comparable dose prescription to targets very close to OAR is described.
  
  
  METHODS
  An intersection volume of a planning risk volume (PRV) with the total planning target volume (PTV) defined the protection volume (PTVSIP). The remainder of the PTV represented the dominant PTV (PTVdom). Planning was performed using IMRT. Dose was prescribed to PTVdomaccording to ICRU in 3, 5, 8, or 12 fractions. Constraints to OARs were expressed as absolute and as equieffective doses at 2 Gy (EQD2). Dose to the gross risk volume of an OAR was to respect constraints. Violation of constraints to OAR triggered a planning iteration at increased fractionation. Dose to PTVSIPwas required to be as high as possible within the constraints to avoid local relapse.
  
  
  RESULTS
  SIP was applied in 6 patients with OAR being large airways (n = 2) or bowel (n = 4) in 3, 5, 8, and 12 fractions in 1, 3, 1, and 1 patients, respectively. PTVs were 14.5-84.9 ml and PTVSIP1.8-3.9 ml (2.9-13.4 % of PTV). Safety of the plans was analyzed from the absolute dose-volume histogram (dose to ml). The steepness of dose fall-off could be determined by comparing the dose constraints to the PRVs with those to the OARs (Wilcoxon test p = 0.001). Constraints were respected for the corresponding OARs. All patients had local control at a median 9 month follow-up and toxicity was low.
  
  
  CONCLUSIONS
  SIP results in a median dose of ≥100 % to PTV, to achieve high local control and low toxicity. Longer follow-up is required to verify results and a prospective clinical trial is currently testing this new approach in chest and abdomen stereotactic body radiotherapy.
authors.affiliation: Department of Radiation Oncology, University Hospitals Freiburg, Freiburg, Deutschland. thomas.brunner@uniklinik-freiburg.de.|Partner Site Freiburg, German Cancer Consortium (DKTK), Heidelberg, Germany. thomas.brunner@uniklinik-freiburg.de.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Brunner
authors.affiliation: Department of Radiation Oncology, University Hospitals Freiburg, Freiburg, Deutschland.|Partner Site Freiburg, German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Ursula
authors.initials: U
authors.lastname: Nestle
authors.affiliation: Department of Radiation Oncology, University Hospitals Freiburg, Freiburg, Deutschland.|Partner Site Freiburg, German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Adebahr
authors.affiliation: Department of Radiation Oncology, University Hospitals Freiburg, Freiburg, Deutschland.|Partner Site Freiburg, German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Eleni
authors.initials: E
authors.lastname: Gkika
authors.affiliation: Department of Radiation Oncology, University Hospitals Freiburg, Freiburg, Deutschland.|Partner Site Freiburg, German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Wiehle
authors.affiliation: Department of Radiation Oncology, University Hospitals Freiburg, Freiburg, Deutschland.|Partner Site Freiburg, German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Dimos
authors.initials: D
authors.lastname: Baltas
authors.affiliation: Department of Radiation Oncology, University Hospitals Freiburg, Freiburg, Deutschland.|Partner Site Freiburg, German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Anca-Ligia
authors.initials: AL
authors.lastname: Grosu
mesh_terms: D004307:Dose-Response Relationship, Radiation; D006801:Humans; D009369:Neoplasms / Q000150:complications / Q000532:radiotherapy*; D059351:Organ Sparing Treatments; D058958:Organs at Risk / Q000528:radiation effects*; D000069473:Radiation Dose Hypofractionation; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control*; D011835:Radiation Protection / Q000379:methods; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: Efficacy; Intensity-modulated radiotherapy; Organs at risk; Stereotactic body radiation therapy; Toxicity