title: Estimating the value of surgical clips for target volume delineation in external beam partial breast radiotherapy.
abstract: OBJECTIVE
  To investigate the role of surgical clips in defining the clinical target volume (CTV) for three-dimensional conformal external beam radiotherapy-partial breast irradiation (3D-CRT-PBI) using preoperative computed tomography scans.
  
  
  METHODS
  A group of patients with early breast cancer underwent conservative surgery with placement of surgical titanium clips (at least three clips required). All patients had a treatment planning computed tomography simulation before (CT1) and after surgery (CT2). The two sets of images were co-registered with a match point registration. The relationship between the clips-based CTV for PBI delineated on CT2 and the initial tumour location on CT1 was studied, evaluating the percentage of intersection volume.
  
  
  RESULTS
  Twenty-eight patients participated in this study. In total, 13 patients (46.4%) had an intersection volume ≥ 50% and 10 patients (35.7%) had complete intersection (intersection volume = 100%). An increased median intersection volume was observed in patients with more than six clips (P = 0.007) and in patients with a larger portion of breast volume covered by the PBI-CTV (CTV/BV; P = 0.010). Intersection volume increased with the number of clips, after adjustment for CTV/BV (linear coefficient = 5.1693; P = 0.043). Also, a maximum distance from the chest wall ≤0.7 cm and CTV/BV > 9.5% were found to be predictors of an intersection volume ≥50% (area under the curve 0.841; confidence interval 0.649-0.952; P < 0.0001; area under the curve 0.800; confidence interval 0.607-0.926; P = 0.0004) and of an intersection volume of 100% (area under the curve 0.776, confidence interval 0.573-0.916, P = 0.046; area under the curve 0.752, confidence interval 0.536-0.935; P = 0.032).
  
  
  CONCLUSIONS
  Titanium clips are essential and six or more increase the accuracy of tumour bed delineation for PBI; also the primary tumour location as well as the percentage of volume of breast covered by PBI-CTV may influence the correct delineation of PBI-CTV.
authors.affiliation: Radiation Oncology, Campus Bio-Medico University, Rome, Italy. Electronic address: e.ippolito@unicampus.it.
authors.forename: E
authors.initials: E
authors.lastname: Ippolito
authors.affiliation: Radiation Oncology, Campus Bio-Medico University, Rome, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Trodella
authors.affiliation: Radiation Oncology, Campus Bio-Medico University, Rome, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Silipigni
authors.affiliation: Radiation Oncology, Campus Bio-Medico University, Rome, Italy.
authors.forename: R M
authors.initials: RM
authors.lastname: D'Angelillo
authors.affiliation: Radiation Oncology, Campus Bio-Medico University, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Di Donato
authors.affiliation: Radiation Oncology, Campus Bio-Medico University, Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Fiore
authors.affiliation: Department of Senology, Campus Bio-Medico University, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Grasso
authors.affiliation: Department of Senology, Campus Bio-Medico University, Rome, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Angelini
authors.affiliation: Radiation Oncology, Campus Bio-Medico University, Rome, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Ramella
authors.affiliation: Department of Senology, Campus Bio-Medico University, Rome, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Altomare
mesh_terms: D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D011379:Prognosis; D011880:Radiotherapy Planning, Computer-Assisted; D013525:Surgical Instruments / Q000706:statistics & numerical data; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
keywords: Partial breast irradiation; surgical clips