title: Clinical Significance of Accounting for Tissue Heterogeneity in Permanent Breast Seed Implant Brachytherapy Planning.
abstract: OBJECTIVE
  The inhomogeneity correction factor (ICF) method provides heterogeneity correction for the fast calculation TG43 formalism in seed brachytherapy. This study compared ICF-corrected plans to their standard TG43 counterparts, looking at their capacity to assess inadequate coverage and/or risk of any skin toxicities for patients who received permanent breast seed implant (PBSI).
  
  
  METHODS
  Two-month postimplant computed tomography scans and plans of 140 PBSI patients were used to calculate dose distributions by using the TG43 and the ICF methods. Multiple dose-volume histogram (DVH) parameters of clinical target volume (CTV) and skin were extracted and compared for both ICF and TG43 dose distributions. Short-term (desquamation and erythema) and long-term (telangiectasia) skin toxicity data were available on 125 and 110 of the patients, respectively, at the time of the study. The predictive value of each DVH parameter of skin was evaluated using the area under the receiver operating characteristic (ROC) curve for each toxicity endpoint.
  
  
  RESULTS
  Dose-volume histogram parameters of CTV, calculated using the ICF method, showed an overall decrease compared to TG43, whereas those of skin showed an increase, confirming previously reported findings of the impact of heterogeneity with low-energy sources. The ICF methodology enabled us to distinguish patients for whom the CTV V100 and V90 are up to 19% lower compared to TG43, which could present a risk of recurrence not detected when heterogeneity are not accounted for. The ICF method also led to an increase in the prediction of desquamation, erythema, and telangiectasia for 91% of skin DVH parameters studied.
  
  
  CONCLUSIONS
  The ICF methodology has the advantage of distinguishing any inadequate dose coverage of CTV due to breast heterogeneity, which can be missed by TG43. Use of ICF correction also led to an increase in prediction accuracy of skin toxicities in most cases.
authors.affiliation: Medical Biophysics Department, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Ontario, Canada.
authors.forename: Shahram
authors.initials: S
authors.lastname: Mashouf
authors.affiliation: Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Ontario, Canada.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Fleury
authors.affiliation: Medical Biophysics Department, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Priscilla
authors.initials: P
authors.lastname: Lai
authors.affiliation: Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Ontario, Canada; Radiotherapy Unit, School of Medicine, Departamento de Hemato-oncologia, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Tomas
authors.initials: T
authors.lastname: Merino
authors.affiliation: Medical Biophysics Department, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Eli
authors.initials: E
authors.lastname: Lechtman
authors.affiliation: Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors.forename: Alex
authors.initials: A
authors.lastname: Kiss
authors.affiliation: Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Ontario, Canada.
authors.forename: Claire
authors.initials: C
authors.lastname: McCann
authors.affiliation: Medical Biophysics Department, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Ontario, Canada; Radiation Oncology Department, Erasmus Medical Center, Cancer Institute, Rotterdam, the Netherlands. Electronic address: j.p.pignol@erasmusmc.nl.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pignol
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008875:Middle Aged; D011855:Radiodermatitis / Q000473:pathology*; D011859:Radiography; D012867:Skin / Q000528:radiation effects