Introduction

• MRI associated with high direct and indirect costs
  • conventional protocols time consuming to acquire and read
• limited access to screening MRI

Introduction

• Propose abbreviated MRI protocol
  • early postcontrast period only
  • MIP for fast overview of imaging volume
• Reduce time and cost associated with screening breast MRI
• Increase access

Methods - design

• Prospective, 2009 - 2010
• Hypothesized abbreviated protocol (AP) associated with reduced diagnostic accuracy
• May be worth it for increased speed/decreased cost

Methods - protocol

• T1 pre
• T1 post (1st acquisition)
• T1 subtracted
• MIP
• T1 post (2nd acquisition)
• T1 post (3rd acquisition)
• T1 post (4th acquisition)
• T1 post (5th acquisition)
• Coronal T1
• Axial T2

Methods - inclusion

• Women referred for screening MRI on clinical grounds
  • 24% Dense breast tissue
  • 26% Family history
  • 50% Personal history (screening contralateral breast)

Methods - interpretation

• Two readers, 18 and 6 years experience
• Images read immediately
  • 1st with AP
    • MIPs read first, recorded presence of abnormal enhancement
    • then rest of AP, given BI-RADS category
  • then with FDP (full diagnostic protocol)
• Time to establish diagnosis recorded

Results - participants

• 443 women (163 underwent 2 annual screening rounds)
• 606 MRIs
• 82% of exams in women with mildly or moderately increased risk
• All were asymptomatic and had negative or benign mammogram at time of MRI
• 427 of 606 had negative or benign US

Results - cancer yield

• 11 cancers diagnosed (incidence = 2.5%)
  • 4 DCIS
  • 7 invasive
  • All had (false) negative or benign mammograms
  • 10 of 11 had (false) negative or benign US, 11th had negative targeted US at site of MRI detected cancer
• 8 high-risk lesions
  • 3 papillomas
  • 2 LCIS
  • 2 ADH
  • 1 radial scar

Results - timing

• Acquisition time
  • AP: 3 m, 4 s
  • FDP: 17 m, 4 s
• Reading time
  • MIP: 2.8 s
  • AP: 28 s

Results - diagnostic accuracy

p=0.317

Discussion

• Cancer yield and diagnostic accuracy equivalent between abbreviated and full protocols
• Substantially reduced time of acquisition and reading
• NPV of MIPs alone 99.8%
• Sens/spec of AP identical to FDP

Discussion

• FDP mainly needed for lesion characterization
• 38% of BI-RADS 3 lesions diagnosed on FAST images downgraded to BI-RADS 2 after reading full protocol
  • Will decreased costs of AP justify increase in BI-RADS 3 diagnoses?

Discussion - limitations

• High volume MRI readers, perhaps not transferrable to community practice

Editorial - Elizabeth Morris

• MRI superior to mammography and US
  • Likelihood of finding cancer at biopsy < 10% if performed on basis of US findings, 30% if on basis of MRI findings
  • MRI geared to detect more biologically relevant cancers (neovascularity, inflammation)

Editorial

• Currently, MRI limited to high risk populations
  • Limited access
  • expensive
  • time-consuming

Editorial

• FAST MRI could reduce barriers to MRI screening
• MRI screening should be offered to all eligible patients
• MRI should be next additional screening modality, not US