title: Mammographic density and the risk of breast cancer recurrence after breast-conserving surgery.
abstract: BACKGROUND
  Women with invasive breast cancer who are treated with breast-conserving surgery and radiotherapy face a cumulative risk of local disease recurrence of approximately 10% at 10 years. To the authors' knowledge, the role of mammographic density as a risk factor for the development of local recurrence has not been thoroughly evaluated to date.
  
  
  METHODS
  Medical records were reviewed for 335 patients who underwent breast-conserving surgery for invasive breast cancer and for whom a pretreatment mammogram was available. Information was recorded concerning mammographic density as well as tumor features, patient characteristics, and adjuvant treatments received. Patients were categorized for mammographic density based on the Wolfe classification as either low (<25% density), intermediate (25-50% density), or high (>50% density). A multivariate survival analysis was conducted using the Cox proportional hazards model with local disease recurrence as the primary endpoint.
  
  
  RESULTS
  Patients in the high mammographic density group experienced a much greater risk of local disease recurrence compared with women with the least dense breasts (10-year actuarial risks: 21% vs 5%; hazards ratio [HR], 5.7 [95% confidence interval, 1.6-20; P=.006]). The difference in the rates of disease recurrence at 10 years was pronounced for women who did not receive radiotherapy (40% vs 0% for patients with >50% density and <25% density, respectively; P<.0001).
  
  
  CONCLUSIONS
  Mammographic breast density is an important risk factor for local breast cancer recurrence among women not receiving breast irradiation. Mammographic density should be taken into consideration when stratifying patients for clinical trials of partial breast radiotherapy. If confirmed, mammographic density might be used to help determine which patients might benefit from radiotherapy.
authors.affiliation: Department of Surgery, University Health Network, and Department of Radiology, Women's College Hospital, Toronto, Ontario, Canada.
authors.forename: Tulin
authors.initials: T
authors.lastname: Cil
authors.forename: Eve
authors.initials: E
authors.lastname: Fishell
authors.forename: Wedad
authors.initials: W
authors.lastname: Hanna
authors.forename: Ping
authors.initials: P
authors.lastname: Sun
authors.forename: Ellen
authors.initials: E
authors.lastname: Rawlinson
authors.forename: Steven A
authors.initials: SA
authors.lastname: Narod
authors.forename: David R
authors.initials: DR
authors.lastname: McCready
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy / Q000601:surgery; D005260:Female; D006801:Humans; D008327:Mammography; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D011379:Prognosis; D012307:Risk Factors