ParticipantsCarrie B. Hruska, PhD, Rochester, MN (Abstract Co-Author) Institutional license agreement, CMR Naviscan Corporation
Katie N. Hunt, MD, Rochester, MN (Presenter) Nothing to Disclose
Matthew Johnson, Rochester, MN (Abstract Co-Author) Nothing to Disclose
Amy Lynn Conners, MD, Rochester, MN (Abstract Co-Author) Nothing to Disclose
Michael K. O'Connor, PhD, Rochester, MN (Abstract Co-Author) Royalties, Gamma Medica, Inc
Deborah J. Rhodes, MD, Rochester, MN (Abstract Co-Author) Nothing to Disclose
Dietlind Wahner-Roedler, MD, Rochester, MN (Abstract Co-Author) Nothing to Disclose
Molecular breast imaging (MBI), which shows uptake of Tc-99m sestamibi in metabolically-active tissue, has been proposed as a tool for determining whether biopsy of mammographically-detected lesions is necessary. Here, our goal was to evaluate the diagnostic accuracy of MBI in patients with suspicious calcifications on mammography.
METHOD AND MATERIALSWomen scheduled to undergo stereotactic biopsy of calcifications detected on 2D mammography were prospectively enrolled to undergo MBI prior to biopsy. MBI was performed with injection of Tc-99m sestamibi and a dedicated gamma camera. A breast radiologist interpreted MBI in conjunction with mammography.
RESULTSIn 71 women studied, 76 discrete areas of calcifications were identified for biopsy, of which pre-biopsy MBI was positive in 17/76 (22%). Of 76 calcification lesions, 24 (32%) were malignant, including 20 DCIS and 4 invasive ductal cancer; MBI was positive in 10/20 (50%) DCIS and 2/4 (50%) invasive cancers. In 21 cancers with calcification morphology of amorphous, coarse heterogeneous, or fine pleomorphic (BI-RADS 4B), MBI was positive in 12/21 (57%), while in three cancers with fine linear or fine linear branching calcifications (BI-RADS 4C), MBI was negative in all 3 (p=0.06). Calcification distribution was more varied for the MBI-positive cancers (0 regional, 7 grouped, 1 linear, 4 segmental) than for the MBI-negative cancers (1 regional, 10 grouped, 1 linear, 0 segmental) (p=0.14). The median pathologic size for MBI-positive cancers was 1.5 cm (range=0.5-3.2 cm) compared to 0.9 cm (range=0.1-2.0 cm) for MBI-negative cancers (p=0.09). Beyond calcification lesions, detection of non-mass focal areas of uptake on MBI led to additional biopsies of 6 sites, of which 2 were malignant (DCIS). The overall positive and negative predictive values of MBI were 61% (14/23) and 81% (48/59), respectively.
CONCLUSIONMBI has insufficient negative predictive value to be used for identifying calcifications in which biopsy could be avoided. However, MBI can reveal additional sites of mammographically-occult disease.
CLINICAL RELEVANCE/APPLICATIONNegative findings on MBI should not be used to avoid biopsy of suspicious calcifications on mammography.