Journal club: molecular breast imaging at reduced radiation dose for supplemental screening in mammographically dense breasts.
Level 3 - non-randomized controlled study
Prospective paired non-randomized diagnostic cohort study
PubMed 25615744 · doi:10.2214/AJR.14.13357
What was done
In a prospective screening cohort, 1,651 asymptomatic women with mammographically dense breasts underwent both screening mammography and adjunct low-dose molecular breast imaging (MBI) using 300-MBq (99m)Tc-sestamibi with a direct-conversion cadmium zinc telluride gamma camera. Mammography and MBI were interpreted independently. Diagnostic performance metrics—including cancer detection rate, sensitivity, specificity, recall rate, biopsy rate, and positive predictive value of biopsies performed (PPV3)—were assessed in 1,585 participants with a complete reference standard.
What was found
Among 1,585 participants with complete follow-up, 21 were diagnosed with cancer (2 by mammography only, 14 by MBI only, 3 by both, 2 by neither). Of the 14 cancers detected only by MBI, 11 were invasive (median size, 0.9 cm; range, 0.5–4.1 cm; 9/11 node-negative). Adding MBI to mammography increased the overall cancer detection rate from 3.2 to 12.0 per 1,000 screened (p < 0.001; supplemental yield 8.8) and invasive cancer detection from 1.9 to 8.8 per 1,000 (p < 0.001), while DCIS detection changed from 1.3 to 3.2 per 1,000 (p = 0.250). For mammography alone versus combined imaging, sensitivity was 24% vs 91% (p < 0.001), specificity was 89% vs 83% (p < 0.001), PPV3 was 25% vs 28% (p = 0.70), recall rate was 11.0% vs 17.6% (p < 0.001), and biopsy rate was 1.3% vs 4.2% (p < 0.001).
Why it matters
Supplemental low-dose molecular breast imaging substantially improves the detection of small, node-negative invasive breast cancers in dense breasts at an effective dose of 2.4 mSv, though at the expense of higher recall and biopsy rates.
Limits
The study is a non-randomized paired screening cohort without long-term survival or interval cancer outcome data. Adding MBI significantly increased false-positive recalls, biopsies, and total ionizing radiation exposure.
Cited by
- contradicts Molecular breast imaging (MBI) delivered approximately 20 to 30 millisieverts of radiation.