title: A clip-based protocol for breast boost radiotherapy provides clear target visualisation and demonstrates significant volume reduction over time.
abstract: BACKGROUND
  The clinical target volume (CTV) for early stage breast cancer is difficult to clearly identify on planning computed tomography (CT) scans. Surgical clips inserted around the tumour bed should help to identify the CTV, particularly if the seroma has been reabsorbed, and enable tracking of CTV changes over time.
  
  
  METHODS
  A surgical clip-based CTV delineation protocol was introduced. CTV visibility and its post-operative shrinkage pattern were assessed. The subjects were 27 early stage breast cancer patients receiving post-operative radiotherapy alone and 15 receiving post-operative chemotherapy followed by radiotherapy. The radiotherapy alone (RT/alone) group received a CT scan at median 25 days post-operatively (CT1rt) and another at 40 Gy, median 68 days (CT2rt). The chemotherapy/RT group (chemo/RT) received a CT scan at median 18 days post-operatively (CT1ch), a planning CT scan at median 126 days (CT2ch), and another at 40 Gy (CT3ch).
  
  
  RESULTS
  There was no significant difference (P = 0.08) between the initial mean CTV for each cohort. The RT/alone cohort showed significant CTV volume reduction of 38.4% (P = 0.01) at 40 Gy. The Chemo/RT cohort had significantly reduced volumes between CT1ch: median 54 cm(3) (4-118) and CT2ch: median 16 cm(3), (2-99), (P = 0.01), but no significant volume reduction thereafter.
  
  
  CONCLUSIONS
  Surgical clips enable localisation of the post-surgical seroma for radiotherapy targeting. Most seroma shrinkage occurs early, enabling CT treatment planning to take place at 7 weeks, which is within the 9 weeks recommended to limit disease recurrence.
authors.affiliation: Department of Radiation Oncology, Northern Sydney Cancer Centre, Royal North Shore Hospital Sydney, New South Wales, Australia.
authors.forename: Lorraine
authors.initials: L
authors.lastname: Lewis
authors.affiliation: Department of Radiation Oncology, Northern Sydney Cancer Centre, Royal North Shore Hospital Sydney, New South Wales, Australia ; Faculty of Health Sciences, University of Sydney Sydney, New South Wales, Australia.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Cox
authors.affiliation: Department of Radiation Oncology, Northern Sydney Cancer Centre, Royal North Shore Hospital Sydney, New South Wales, Australia.
authors.forename: Marita
authors.initials: M
authors.lastname: Morgia
authors.affiliation: Faculty of Health Sciences, University of Sydney Sydney, New South Wales, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Atyeo
authors.affiliation: Department of Radiation Oncology, Northern Sydney Cancer Centre, Royal North Shore Hospital Sydney, New South Wales, Australia.
authors.forename: Gillian
authors.initials: G
authors.lastname: Lamoury
keywords: Breast cancer; radiotherapy; seroma; surgical clips