title: Mixed modality treatment planning of accelerated partial breast irradiation: to improve complex dosimetry cases.
abstract: BACKGROUND
  Although 3D-conformal accelerated partial breast irradiation (APBI) is widely used, several questions still remain such as what are the optimal treatment planning modalities. Indeed, some patients may have an unfavorable anatomy and/or inadequate dosimetric constraints could be fulfilled ("complex cases"). In such cases, we wondered which treatment planning modality could be applied to achieve 3D-conformal APBI (2 mini-tangents and an "en face" electron field or non-coplanar photon multiple fields; or a mixed technique combining non-coplanar photon multiple fields with an "en face" electron beam).
  
  
  METHODS
  From October 2007 to March 2010, 55 patients with pT1N0 breast cancer were enrolled in a phase II APBI trial. Among them, 7 patients were excluded as they were considered as "complex cases". A dosimetric comparison was performed according to the 3 APBI modalities mentioned above and assessed: planning treatment volume (PTV) coverage, PTV/whole breast ratio, lung and heart distance within irradiated field and exposure of organs at risk (OAR).
  
  
  RESULTS
  Adequate PTV coverage was obtained with the 3 different treatment planning. Regarding OAR exposure, the "mixed technique" seemed to reduce the volume of non-target breast tissue in 4 cases compared to the other techniques (in only 1 case), with the mean V50% at 44.9% (range, 13.4 - 56.9%) for the mixed modality compared to 51.1% (range, 22.4 - 63.4%) and 51.8% (range, 23.1 - 59.5%) for the reference and non-coplanar techniques, respectively. The same trend was observed for heart exposure.
  
  
  CONCLUSIONS
  The mixed technique showed a promising trend of reducing the volume of non-target breast tissue and heart exposure doses in APBI "complex cases".
authors.affiliation: Department of Radiation Oncology, Institut Gustave Roussy, 94805 Villejuif, France.
authors.forename: Mohamed
authors.initials: M
authors.lastname: El Nemr
authors.forename: Steve
authors.initials: S
authors.lastname: Heymann
authors.forename: Rodolfe
authors.initials: R
authors.lastname: Verstraet
authors.forename: Bruno
authors.initials: B
authors.lastname: Biron
authors.forename: Fares
authors.initials: F
authors.lastname: Azoury
authors.forename: Hugo
authors.initials: H
authors.lastname: Marsiglia
authors.forename: Céline
authors.initials: C
authors.lastname: Bourgier
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D018714:Radiotherapy, Adjuvant / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods
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