title: Tumor bed segmentation: first step for partial breast irradiation.
abstract: BACKGROUND
  In breast IMRT simultaneous integrated boost (SIB) treatment and accelerated partial breast irradiation (APBI), proper delineation of the tumor bed is necessary. Conservative oncoplastic surgery causes changes in peritumoral breast tissue that complicates locating the site of the tumor. Nevertheless, there are still centers that do not use surgical clips to delineate the site. This study aims to show how the lack of clips affects the techniques of SIB and APBI in terms of dose distribution and safety margins in the tumor bed.
  
  
  METHODS
  On 30 patients, the defining of the tumor bed obtained from the pre-surgery CT scan to that outlined on the basis of clips on the post-surgery CT was compared. Tumor bed deviation from the original tumor site was quantified. In addition, the margins to the original tumor site necessary to guarantee the coverage of the tumor bed were calculated.
  
  
  RESULTS
  Variations were detected in the distances between geometric centers of the PTV (minimum 0.5-maximum 3 cm). The maximum margin necessary to include the entire tumor bed was 4.5 cm. Lesions located in the upper outer quadrant required the widest margins. If margins are not added, the tumor bed volume defined with clips will be underdosed.
  
  
  CONCLUSIONS
  The definition of the tumor bed based on studies before surgery does not have the necessary accuracy. Clips need to be placed in the surgical bed to identify the changes occurring after the restorative mammoplasty. Without clips, SIB and APBI are not safe.
authors.affiliation: Radiation Oncology Department, ERESA, Hospital General Universitario de Valencia, Avenida Tres Cruces no 2, Valencia, Spain. agonzalez@eresa.com
authors.forename: Amparo
authors.initials: A
authors.lastname: González Sanchis
authors.forename: Luis
authors.initials: L
authors.lastname: Brualla González
authors.forename: Carlos
authors.initials: C
authors.lastname: Fuster Diana
authors.forename: Jose Carlos
authors.initials: JC
authors.lastname: Gordo Partearroyo
authors.forename: Andres
authors.initials: A
authors.lastname: Garcia-Vilanova Comas
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Lopez Torrecilla
authors.forename: Joan
authors.initials: J
authors.lastname: Roselló Ferrando
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001940:Breast / Q000473:pathology / Q000528:radiation effects / Q000601:surgery; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental / Q000379:methods*; D008875:Middle Aged; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted