Supplemental molecular breast imaging more than doubled invasive cancer detection rates in women with dense breasts.
Adding molecular breast imaging (MBI) to standard digital breast tomosynthesis (DBT) screening more than doubled the detection of invasive breast cancers among women with dense breast tissue, according to results from the multicenter Density MATTERS Trial published in Radiology and led by Carrie Hruska, PhD, of the Mayo Clinic.1,2
Dense breast tissue, present in nearly half of women in the United States, can obscure cancers on mammograms and increase the risk of delayed diagnosis. MBI, a functional imaging technique using technetium 99m sestamibi, highlights radiotracer uptake in metabolically active lesions, helping to detect cancers masked on mammography.
Hruska explained, “A mammogram is an important screening test that has been proven beneficial. But we've learned that in areas of dense breast tissue, breast cancers can hide from detection on a mammogram until they reach an advanced size. Our research focuses on detecting the most lethal cancers, which can include invasive tumors that grow quickly. If these are detected earlier, we likely can save more lives.”
The prospective, multiyear Density MATTERS Trial enrolled 2978 women aged 40 to 75 years with dense breasts across 5 US sites from 2017 to 2022. Each participant underwent 2 annual screening rounds combining MBI and DBT. Radiologists independently interpreted the MBI and DBT images, blinded to the other modality’s results.
The study’s primary endpoint was the incremental invasive cancer detection rate (CDR) from supplemental MBI, reported as cancers per 1000 screenings. Secondary outcomes included overall CDR, recall rate, and biopsy rate.
At the first annual screening, the invasive cancer detection rate increased from 3.0 per 1000 with DBT alone to 7.7 per 1000 with DBT plus MBI—a 2.5-fold improvement. At the second annual screening, invasive detection increased from 1.5 per 1000 with DBT to 3.9 per 1000 with the combination.
Overall, 35 cancers were detected at the first screening with DBT plus MBI compared to 15 with DBT alone. During the second round, 24 cancers were found with the combination compared to 15 with DBT alone.
Importantly, 29 women had cancers detected only with MBI, 72% of which were invasive and 90% node negative, with a median tumor size of 0.9 cm. The interval cancer rate remained low—0.7 and 0.8 per 1000 screenings at years 1 and 2, respectively.
The addition of MBI initially increased the recall rate from 8.6% to 17.9% at the first screening but fell to 13.8% in the second round, suggesting improved efficiency over time. Similarly, biopsy rates rose modestly, and no serious adverse events were reported.
“MBI is a fairly simple, low-cost, and safe option for women who have dense breasts and are seeking a supplemental screening test,” said Hruska. Current availability in the United States is limited to approximately 30 sites, including Mayo Clinic campuses in Rochester, Phoenix, and Jacksonville, as well as Mayo Clinic Health System locations in Wisconsin.
While supplemental MRI remains the American College of Radiology’s preferred option for women with dense breasts, cost, contrast requirements, and patient tolerance can limit its use. MBI provides an alternative for those unable or unwilling to undergo MRI, with similar detection improvements but lower cost and simpler administration.
To increase accessibility, Hruska’s team is developing a new algorithm to reduce imaging time from 40 minutes to 20 minutes or less, improving patient comfort and throughput.
In summary, the Density MATTERS Trial demonstrated that adding MBI to DBT significantly improves early detection of invasive cancers in women with dense breasts while maintaining manageable recall rates. The findings support MBI as a viable, safe, and cost-effective adjunct to mammography in this high-prevalence population.
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