title: Volumetric modulated arc therapy for synchronous bilateral whole breast irradiation - A case study.
abstract: OBJECTIVE
  The treatment planning of bilateral breast irradiation (BBI) is a challenging task. The overlapping of tangential fields is usually unavoidable without compromising the target coverage. The purpose of this study was to investigate the technical feasibility and benefits of a single isocentre volumetric modulated arc therapy (VMAT) in BBI.
  
  
  METHODS
  Two women with bilateral breast cancer were included in this case study. The first patient (Pat#1) underwent a bilateral breast-conserving surgery and sentinel lymph node biopsy. The second patient (Pat#2) underwent a bilateral ablation and axillary lymph node dissection. Planning target volumes (PTV) and organs at risk were delineated on CT images. VMAT plans were created with four (two for both sides, Pat#1) or two (one for each breast, Pat#2) separate VMAT fields. Subsequently, traditional tangential field plans were generated for each patient and the dosimetric parameters were compared.
  
  
  RESULTS
  The treatment times of the patients with VMAT were less than 15 min with daily CBCT imaging. When compared to the standard tangential field technique, the VMAT plans improved the PTV dose coverage and dose homogeneity with improved sparing of lungs and heart. With traditional field arrangement, the overlapping of the tangential fields was inevitable without significantly compromising the target coverage, whereas with VMAT the hotspots were avoided. The patients were treated with the VMAT technique and no acute skin toxicity was observed with either of the patients.
  
  
  CONCLUSIONS
  A single isocentre VMAT technique has been implemented clinically for BBI. With the VMAT techniques, the dose delivery was quick and the hotspots in the field overlapping areas were avoided. The PTV dose coverage was superior in VMAT plans when compared with conventional tangential technique plans.
authors.affiliation: Cancer Center, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Jan
authors.initials: J
authors.lastname: Seppälä
authors.affiliation: Cancer Center, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Janne
authors.initials: J
authors.lastname: Heikkilä
authors.affiliation: Cancer Center, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Kimmo
authors.initials: K
authors.lastname: Myllyoja
authors.affiliation: Cancer Center, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Kristiina
authors.initials: K
authors.lastname: Koskela
keywords: Bilateral breast cancer; Field overlapping; Hotspots; Radiotherapy; VMAT