title: Accelerated partial breast irradiation using robotic radiotherapy: a dosimetric comparison with tomotherapy and three-dimensional conformal radiotherapy.
abstract: BACKGROUND
  Accelerated partial breast irradiation (APBI) is a new breast treatment modality aiming to reduce treatment time using hypo fractionation. Compared to conventional whole breast irradiation that takes 5 to 6 weeks, APBI is reported to induce worse cosmetic outcomes both when using three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT). These late normal tissue effects may be attributed to the dose volume effect because a large portion of the non-target breast tissue volume (NTBTV) receives a high dose. In the context of APBI, non-coplanar beams could spare the NTBTV more efficiently. This study evaluates the dosimetric benefit of using the Cyberknife (CK) for APBI in comparison to IMRT (Tomotherapy) and three dimensional conformal radiotherapy (3D-CRT).
  
  
  METHODS
  The possibility of using surgical clips, implanted during surgery, to track target movements is investigated first. A phantom of a female thorax was designed in-house using the measurements of 20 patients. Surgical clips of different sizes were inserted inside the breast. A treatment plan was delivered to the mobile and immobile phantom. The motion compensation accuracy was evaluated using three radiochromic films inserted inside the breast. Three dimensional conformal radiotherapy (3D-CRT), Tomotherapy (TOMO) and CK treatment plans were calculated for 10 consecutive patients who received APBI in Lille. To ensure a fair comparison of the three techniques, margins applied to the CTV were set to 10 mm. However, a second CK plan was prepared using 3 mm margins to evaluate the benefits of motion compensation.
  
  
  RESULTS
  Only the larger clips (VITALITEC Medium-Large) could be tracked inside the larger breast (all gamma indices below 1 for 1 % of the maximum dose and 1 mm). All techniques meet the guidelines defined in the NSABP/RTOG and SHARE protocols. As the applied dose volume constraints are very strong, insignificant dosimetric differences exist between techniques regarding the PTV coverage and the sparing of the lung and heart. However, the CK may be used to reduce high doses received by the NTBTV more efficiently.
  
  
  CONCLUSIONS
  Robotic stereotactic radiotherapy may be used for APBI to more efficiently spare the NTBTV and improve cosmetic results of APBI.
authors.affiliation: Academic Department of Radiation Oncology, Centre Oscar Lambret, 3 rue Frédéric Combemale, BP 307, 59020, LILLE Cedex, France. e-rault@o-lambret.fr.
authors.forename: Erwann
authors.initials: E
authors.lastname: Rault
authors.affiliation: Academic Department of Radiation Oncology, Centre Oscar Lambret, 3 rue Frédéric Combemale, BP 307, 59020, LILLE Cedex, France. t-lacornerie@o-lambret.fr.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lacornerie
authors.affiliation: Academic Department of Radiation Oncology, Centre Oscar Lambret, 3 rue Frédéric Combemale, BP 307, 59020, LILLE Cedex, France. hong_phuong.dang@ec-lille.fr.
authors.forename: Hong-Phuong
authors.initials: HP
authors.lastname: Dang
authors.affiliation: Academic Department of Radiation Oncology, Centre Oscar Lambret, 3 rue Frédéric Combemale, BP 307, 59020, LILLE Cedex, France. f-crop@o-lambret.fr.
authors.forename: Frederik
authors.initials: F
authors.lastname: Crop
authors.affiliation: Academic Department of Radiation Oncology, Centre Oscar Lambret, 3 rue Frédéric Combemale, BP 307, 59020, LILLE Cedex, France. e-lartigau@o-lambret.fr.|CRIStAL, UMR CNRS 9189, Villeneuve d'Ascq, France. e-lartigau@o-lambret.fr.
authors.forename: Eric
authors.initials: E
authors.lastname: Lartigau
authors.affiliation: Academic Department of Radiation Oncology, Centre Oscar Lambret, 3 rue Frédéric Combemale, BP 307, 59020, LILLE Cedex, France. n-reynaert@o-lambret.fr.
authors.forename: Nick
authors.initials: N
authors.lastname: Reynaert
authors.affiliation: Academic Department of Radiation Oncology, Centre Oscar Lambret, 3 rue Frédéric Combemale, BP 307, 59020, LILLE Cedex, France. d-pasquier@o-lambret.fr.|CRIStAL, UMR CNRS 9189, Villeneuve d'Ascq, France. d-pasquier@o-lambret.fr.
authors.forename: David
authors.initials: D
authors.lastname: Pasquier
mesh_terms: D001940:Breast / Q000528:radiation effects*; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D009068:Movement; D019047:Phantoms, Imaging; D011832:Radiation Injuries / Q000517:prevention & control; D011874:Radiometry / Q000379:methods*; D016634:Radiosurgery / Q000379:methods*; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012119:Respiration; D012371:Robotics / Q000379:methods*; D013525:Surgical Instruments