title: Magnetic resonance imaging identifies multifocal and multicentric disease in breast cancer patients who are eligible for partial breast irradiation.
abstract: BACKGROUND
  In this retrospective study, the authors hypothesized that magnetic resonance imaging (MRI) would alter partial breast irradiation (PBI) eligibility by identifying cancers outside the PBI volume compared with mammography alone.
  
  
  METHODS
  Since 2002, MRI was used nonselectively at the authors' institution for the staging of patients with nonmetastatic breast cancer. Of 450 consecutive patients with invasive breast cancer, 110 patients who were eligible for PBI were identified by using criteria outlined by National Surgical Adjuvant Breast and Bowel Project B-39/Radiation Oncology Group trial 0413 based on mammography, ultrasonography, and initial pathology. In that trial, patients were randomized (stage I/II invasive cancers that measured <or=3 cm and <or=3 positive lymph nodes) to receive either whole-breast radiotherapy or PBI. MRI reports were reviewed to determine whether MRI identified secondary lesions 1) within the same quadrant (multifocal), 2) in a different quadrant (multicentric), or 3) in the contralateral breast. These lesions were pathologically proven carcinoma and would have rendered the patient ineligible for PBI.
  
  
  RESULTS
  MRI identified secondary lesions in 10% of patients (95% confidence interval [CI], 4.4%-15.6%). Multifocal disease was identified in 3.6% (95% CI, 1.4%-9%), multicentric disease was identified in 4.5% (95% CI, 2%-10.2%), and contralateral disease was identified in 1.8% (95% CI, 0.5%-6.4%). The proportion of patients with false-positive MRI findings was 4.5% (95% CI, 2%-10.2%). The positive predictive value of MRI was 72.2% (95% CI, 46.4%-89.3%).
  
  
  CONCLUSIONS
  MRI identified frequent secondary cancers that would not be removed routinely by surgery or targeted in the radiation field if treated with PBI. The current data suggest that MRI should be considered to assess PBI eligibility to minimize potential local failures.
authors.affiliation: Department of Radiation and Cellular Oncology, University of Chicago, Chicago, Illinois 60637, USA. hal-hallaq@radonc.uchicago.edu
authors.forename: Hania A
authors.initials: HA
authors.lastname: Al-Hallaq
authors.forename: Loren K
authors.initials: LK
authors.lastname: Mell
authors.forename: Julie A
authors.initials: JA
authors.lastname: Bradley
authors.forename: Lucy F
authors.initials: LF
authors.lastname: Chen
authors.forename: Arif N
authors.initials: AN
authors.lastname: Ali
authors.forename: Ralph R
authors.initials: RR
authors.lastname: Weichselbaum
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Newstead
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Chmura
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy / Q000601:surgery; D018270:Carcinoma, Ductal, Breast / Q000175:diagnosis* / Q000532:radiotherapy / Q000601:surgery; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000175:diagnosis* / Q000532:radiotherapy / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008327:Mammography; D008875:Middle Aged; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies