title: Heart dose reduction in breast cancer treatment with simultaneous integrated boost: Comparison of treatment planning and dosimetry for a novel hybrid technique and 3D-CRT.
abstract: OBJECTIVE
  The present study compares in silico treatment plans of clinically established three-dimensional conformal radiotherapy (3D-CRT) with a hybrid technique consisting of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc radiotherapy (VMAT) during normally fractionated radiation of mammary carcinomas with simultaneous integrated boost on the basis of dose-volume histogram (DVH) parameters.
  
  
  METHODS
  Radiation treatment planning was performed with a hybrid and a 3D-CRT treatment plan for 20 patients. Hybrid plans were implemented with two tangential IMRT fields and a VMAT field in the angular range of the tangents. Verification of the plan was performed with a manufacturer-independent measurement system consisting of a detector array and rotation unit.
  
  
  RESULTS
  The mean values of the heart dose for the entire patient collective were 3.6 ± 2.5 Gy for 3D-CRT and 2.9 ± 2.1 Gy for the hybrid technique (p < 0.01). For the left side (n = 10), the mean values for the left anterior descending artery were 21.8 ± 7.4 Gy for 3D-CRT and 17.6 ± 7.4 Gy for the hybrid technique (p < 0.01). The mean values of the ipsilateral lung were 11.9 ± 1.6 Gy for 3D-CRT and 10.5 ± 1.3 Gy for the hybrid technique (p < 0.01). Calculated dose distributions in the hybrid arm were in good accordance with measured dose (on average 95.6 ± 0.5 % for γ < 1 and 3 %/3 mm). The difference of the mean treatment time per fraction was 7 s in favor of 3D-CRT.
  
  
  CONCLUSIONS
  Compared with the established 3D-CRT technique, the hybrid technique allows for a decrease in dose, particularly of the mean heart and lung dose with comparable target volume acquisition and without disadvantageous low-dose load of contralateral structures. Uncomplicated implementation of the hybrid technique was demonstrated in this context. The hybrid technique combines the advantages of tangential IMRT with the superior sparing of organs at risk by VMAT.
authors.affiliation: Radiological Alliance, Mörkenstrasse 47, 22767, Hamburg, Germany, vincent.joest@radiologische-allianz.de.
authors.forename: Vincent
authors.initials: V
authors.lastname: Jöst
authors.forename: Matthias
authors.initials: M
authors.lastname: Kretschmer
authors.forename: Marcello
authors.initials: M
authors.lastname: Sabatino
authors.forename: Florian
authors.initials: F
authors.lastname: Würschmidt
authors.forename: Jörg
authors.initials: J
authors.lastname: Dahle
authors.forename: Friedrich
authors.initials: F
authors.lastname: Ueberle
authors.forename: Jörn
authors.initials: J
authors.lastname: Lorenzen
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D003131:Combined Modality Therapy / Q000379:methods; D019583:Dose Fractionation, Radiation; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D008875:Middle Aged; D059351:Organ Sparing Treatments / Q000379:methods; D009928:Organ Specificity; D011835:Radiation Protection / Q000379:methods*; D011859:Radiography; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018511:Systems Integration