title: Evaluation of implanted gold seeds for breast radiotherapy planning and on treatment verification: a feasibility study on behalf of the IMPORT trialists.
abstract: OBJECTIVE
  We describe a feasibility study testing the use of gold seeds for the identification of post-operative tumour bed after breast conservation surgery (BCS).
  
  
  METHODS
  Fifty-three patients undergoing BCS for invasive cancer were recruited. Successful use was defined as all six seeds correctly positioned around the tumour bed during BCS, unique identification of all implanted seeds on CT planning scan and ≥ 3 seeds uniquely identified at verification to give couch displacement co-ordinates in 10/15 fractions. Planning target volume (PTV) margin size for four correction strategies were calculated from these data. Variability in tumour bed contouring was investigated with five radiation oncologists outlining five CT datasets.
  
  
  RESULTS
  Success in inserting gold seeds, identifying them at CT planning and using them for on-treatment verification was recorded in 45/51 (88%), 37/38 (97%) and 42/43 (98%) of patients, respectively. The clinicians unfamiliar with CT breast planning consistently contoured larger volumes than those already trained. Margin size ranged from 10.1 to 1.4mm depending on correction strategy.
  
  
  CONCLUSIONS
  It is feasible to implant tumour bed gold seeds during BCS. Whilst taking longer to insert than surgical clips, they have the advantage of visibility for outlining and verification regardless of the ionising radiation beam quality. Appropriate correction strategies enable margins of the order of 5mm as required by the IMPORT trials however, tackling clinician variability in contouring is important.
authors.affiliation: Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK. charlotte.coles@addenbrookes.nhs.uk
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Coles
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Harris
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Donovan
authors.forename: Peter
authors.initials: P
authors.lastname: Bliss
authors.forename: Philip M
authors.initials: PM
authors.lastname: Evans
authors.forename: Jamie
authors.initials: J
authors.lastname: Fairfoul
authors.forename: Christine
authors.initials: C
authors.lastname: Mackenzie
authors.forename: Christine
authors.initials: C
authors.lastname: Rawlings
authors.forename: Isabel
authors.initials: I
authors.lastname: Syndikus
authors.forename: Nicola
authors.initials: N
authors.lastname: Twyman
authors.forename: Joana
authors.initials: J
authors.lastname: Vasconcelos
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Vowler
authors.forename: Jenny S
authors.initials: JS
authors.lastname: Wilkinson
authors.forename: Robin
authors.initials: R
authors.lastname: Wilks
authors.forename: Gordon C
authors.initials: GC
authors.lastname: Wishart
authors.forename: John
authors.initials: J
authors.lastname: Yarnold
mesh_terms: D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006046:Gold; D006801:Humans; D015412:Mastectomy, Segmental; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D006046:Gold