title: The incidence of fat necrosis in balloon-based breast brachytherapy.
abstract: OBJECTIVE
  To investigate the incidence of and potential risk factors for fat necrosis in high dose-rate (HDR) balloon-based breast brachytherapy (BBB).
  
  
  METHODS
  Fifty-four patients were treated postoperatively with HDR-BBB between May 2007 and December 2010. Median age was 71 years (range: 50-88 years). Median tumor size was 1 cm (range: 0.1-2.7 cm). Forty-four had invasive histology; 43% were grade 1, 24% grade 2, and 15% grade 3. The median margin size was 0.7 cm (range: 0.1-1.5 cm).
  
  
  RESULTS
  With a median follow-up of 2.9 years (range: 0.5-5.2 years), local control was 98% with one in-breast failure, and overall survival was 89%. Fifty percent of patients experienced fat necrosis. Seven patients were symptomatic, with the remainder detected by mammography alone. Two patients required surgical resection with pathology confirming fat necrosis; 1 required i.v. steroids. At 1, 3, and 5 years following treatment, estimated cumulative incidences of fat necrosis were 7.5%, 52.7%, and 60.6%. Breast laterality, location, tumor size, histology, margin size, balloon volume, skin distance, skin dose, and number of dwell positions were not significantly associated with fat necrosis on univariate analysis.
  
  
  CONCLUSIONS
  In this retrospective review of HDR-BBB, we found a 50% incidence of both asymptomatic and symptomatic fat necrosis. Only three patients, however, required intervention. None of the risk factors considered were significantly associated with fat necrosis. Further studies evaluating factors associated with fat necrosis for patients undergoing HDR-BBB are necessary to appropriately assess the risks associated with treatment.
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Jacksonville, FL.
authors.forename: Nitesh N
authors.initials: NN
authors.lastname: Paryani
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Jacksonville, FL.
authors.forename: Laura
authors.initials: L
authors.lastname: Vallow
authors.affiliation: Department of Surgery, Mayo Clinic, Jacksonville, FL.
authors.forename: Wilza
authors.initials: W
authors.lastname: Magalhaes
authors.affiliation: Section of Biostatistics, Mayo Clinic, Jacksonville, FL.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Heckman
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Jacksonville, FL ; Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Siyong
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Jacksonville, FL.
authors.forename: Ashley
authors.initials: A
authors.lastname: Smith
authors.affiliation: Section of Biostatistics, Mayo Clinic, Jacksonville, FL.
authors.forename: Nancy N
authors.initials: NN
authors.lastname: Diehl
authors.affiliation: Department of Surgery, Mayo Clinic, Jacksonville, FL.
authors.forename: Sarah
authors.initials: S
authors.lastname: McLaughlin
keywords: brachytherapy; breast cancer; high-dose rate; necrosis; survival; toxicity
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