title: Equivalent uniform dose for accelerated partial breast irradiation using the MammoSite applicator.
abstract: BACKGROUND
  This study aims to quantify the radiobiology of the MammoSite applicator and examine whether there is a relationship between equivalent uniform dose (EUD) and radiotherapy-associated toxicity.
  
  
  METHODS
  A previously-published version of the linear quadratic (LQ) model, designed to address the impact of dose-gradients in brachytherapy applications, was used to determine the biological effective dose (BED), equivalent dose in 2 Gray per fraction (EQD2) and EUD for the most common fractionation scheme for the MammoSite catheter (34 Gy in 10 fractions prescribed to 1cm from the balloon surface), using a range of balloon sizes in a series of patients treated with single or multiple dwell positions. Toxicity from the MammoSite catheter was assessed and statistical associations with the calculated EUDs were investigated.
  
  
  RESULTS
  The acute- and late-toxicity EUDs respectively range from 34.8-39.4 Gy and 33.4-37.6 Gy, with EUD decreasing as balloon diameter increases and/or the number of dwell positions increases. There was a positive association between EUD and hyperpigmentation and telangiectasia.
  
  
  CONCLUSIONS
  For APBI using the Mammosite applicator, EUD is higher than the marginal prescription dose and, for the dose-fractionation patterns considered here, was associated with acute and late skin toxicity. EUD is a potentially useful parameter to characterize non-uniform dose distributions related to brachytherapy treatments. Further evaluation in future studies is warranted.
authors.affiliation: St. Luke's Cancer Centre, Royal Surrey County Hospital, Guildford, United Kingdom. Electronic address: Alexandra.stewart@nhs.net.
authors.forename: Alexandra J
authors.initials: AJ
authors.lastname: Stewart
authors.forename: Jaroslaw T
authors.initials: JT
authors.lastname: Hepel
authors.forename: Desmond A
authors.initials: DA
authors.lastname: O'Farrell
authors.forename: Phillip M
authors.initials: PM
authors.lastname: Devlin
authors.forename: Lori Lyn
authors.initials: LL
authors.lastname: Price
authors.forename: Roger G
authors.initials: RG
authors.lastname: Dale
authors.forename: David E
authors.initials: DE
authors.lastname: Wazer
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001918:Brachytherapy / Q000009:adverse effects* / Q000295:instrumentation* / Q000379:methods; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D015331:Cohort Studies; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D015412:Mastectomy, Segmental / Q000379:methods; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D011832:Radiation Injuries / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant; D012189:Retrospective Studies; D018570:Risk Assessment; D016896:Treatment Outcome
keywords: Equivalent uniform dose; MammoSite catheter; Radiobiology; Toxicity analysis