title: The effect of dose-volume parameters and interfraction interval on cosmetic outcome and toxicity after 3-dimensional conformal accelerated partial breast irradiation.
abstract: OBJECTIVE
  To evaluate dose-volume parameters and the interfraction interval (IFI) as they relate to cosmetic outcome and normal tissue effects of 3-dimensional conformal radiation therapy (3D-CRT) for accelerated partial breast irradiation (APBI).
  
  
  METHODS
  Eighty patients were treated by the use of 3D-CRT to deliver APBI at our institutions from 2003-2010 in strict accordance with the specified dose-volume constraints outlined in the National Surgical Adjuvant Breast and Bowel Project B39/Radiation Therapy Oncology Group 0413 (NSABP-B39/RTOG 0413) protocol. The prescribed dose was 38.5 Gy in 10 fractions delivered twice daily. Patients underwent follow-up with assessment for recurrence, late toxicity, and overall cosmetic outcome. Tests for association between toxicity endpoints and dosimetric parameters were performed with the chi-square test. Univariate logistic regression was used to evaluate the association of interfraction interval (IFI) with these outcomes.
  
  
  RESULTS
  At a median follow-up time of 32 months, grade 2-4 and grade 3-4 subcutaneous fibrosis occurred in 31% and 7.5% of patients, respectively. Subcutaneous fibrosis improved in 5 patients (6%) with extended follow-up. Fat necrosis developed in 11% of women, and cosmetic outcome was fair/poor in 19%. The relative volume of breast tissue receiving 5%, 20%, 50%, 80%, and 100% (V5-V100) of the prescribed dose was associated with risk of subcutaneous fibrosis, and the volume receiving 50%, 80%, and 100% (V50-V100) was associated with fair/poor cosmesis. The mean IFI was 6.9 hours, and the minimum IFI was 6.2 hours. The mean and minimum IFI values were not significantly associated with late toxicity.
  
  
  CONCLUSIONS
  The incidence of moderate to severe late toxicity, particularly subcutaneous fibrosis and fat necrosis and resulting fair/poor cosmesis, remains high with continued follow-up. These toxicity endpoints are associated with several dose-volume parameters. Minimum and mean IFI values were not associated with late toxicity.
authors.affiliation: Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts, USA. karalynne.kerr@gmail.com
authors.forename: Kara Lynne
authors.initials: KL
authors.lastname: Leonard
authors.forename: Jaroslaw T
authors.initials: JT
authors.lastname: Hepel
authors.forename: Jessica R
authors.initials: JR
authors.lastname: Hiatt
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Dipetrillo
authors.forename: Lori Lyn
authors.initials: LL
authors.lastname: Price
authors.forename: David E
authors.initials: DE
authors.lastname: Wazer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D004954:Esthetics; D005260:Female; D005355:Fibrosis; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D011832:Radiation Injuries / Q000473:pathology; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods*; D012189:Retrospective Studies; D012867:Skin / Q000473:pathology / Q000528:radiation effects*; D016896:Treatment Outcome; D047368:Tumor Burden