title: Clinical characteristics and outcomes of bilateral breast cancer in an Australian cohort.
abstract: OBJECTIVE
  Uncertainty remains about the impact of bilateral breast cancer. Characteristics and outcomes of unilateral and bilateral breast cancer were compared within an Australian multi-institutional cohort.
  
  
  METHODS
  Demographic, tumour and treatment characteristics were compared among unilateral (n = 2336) and bilateral cases (52 synchronous, 35 metachronous) using descriptive analyses. Disease-specific outcomes were investigated using Cox regression modelling to adjust for prognostic and treatment factors.
  
  
  RESULTS
  Factors associated with increased risk of bilateral breast cancer included lobular histology (p = 0.046), family history (p = 0.025) and metropolitan residence (p = 0.006). Mastectomy was more common for bilateral cases (p = 0.001) while radiotherapy was less common (p = 0.015). Index metachronous cases were less likely to receive hormonal therapy (p = 0.001). Five-year survivals for metachronous, synchronous and unilateral cases were 79%, 88% and 94%, respectively. Poorer outcomes remained after adjusting for prognostic factors [HR = 2.26, 1.21-4.21].
  
  
  CONCLUSIONS
  Our results confirm international findings indicating worse outcomes from bilateral compared with unilateral breast cancer.
authors.affiliation: Cancer Council South Australia, PO Box 929, Adelaide, Unley, South Australia 5061, Australia. kbeckmann@cancersa.org.au
authors.forename: K R
authors.initials: KR
authors.lastname: Beckmann
authors.forename: J
authors.initials: J
authors.lastname: Buckingham
authors.forename: P
authors.initials: P
authors.lastname: Craft
authors.forename: J E
authors.initials: JE
authors.lastname: Dahlstrom
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: D
authors.initials: D
authors.lastname: Roder
authors.forename: R
authors.initials: R
authors.lastname: Stuart-Harris
mesh_terms: D001315:Australia; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000473:pathology* / Q000628:therapy; D015331:Cohort Studies; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008875:Middle Aged; D009378:Neoplasms, Multiple Primary / Q000453:epidemiology / Q000473:pathology / Q000628:therapy; D016609:Neoplasms, Second Primary / Q000453:epidemiology / Q000473:pathology / Q000628:therapy; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors