In previous work, Dr. Deborah Rhodes from the Mayo Clinic in Rochester, MN, and colleagues showed that adding MBI -- 20 mCi of technetium-99m (Tc-99m) sestamibi -- to screening mammography increased the diagnostic yield for breast cancer (3.2 per 1,000 for mammography alone versus 10.7 per 1,000 for the combination). For this study, Rhodes' group established radiation dose reduction techniques and then compared the two modalities in women with dense breasts.
The researchers included 1,640 women with heterogeneously or extremely dense breasts who presented for screening mammography; each underwent digital mammography and MBI. MBI exams were performed with 8 mCi of Tc-99m sestamibi and dual-head cadmium zinc telluride detectors. Of the total cohort, 27 cancers were diagnosed in 21 patients:
- MBI alone detected cancer in 17 of 21 women.
- Mammography alone detected cancer in five of 21 women.
- MBI with mammography detected cancer in 19 of 21 women.
The diagnostic yield was three per 1,000 for mammography alone, compared with 11.6 per 1,000 for the combination of MBI and mammography, the researchers found. The additional diagnostic yield of screening low-dose MBI to screening mammography in women with dense breasts remains, even at a lower administered radiation dose, they concluded.
