Low-dose molecular breast imaging effective in supplemental cancer screenings

Cancer detection success rates in women with mammographically dense breasts can be significantly improved through molecular imaging techniques, even using a reduced radiation dose, according to a study published in the February issue of the American Journal of Roentgenology.

Past studies have shown that digital screening mammography methods have limited effectiveness in detecting cancer among women with dense breasts. As this represents approximately half of the screening-aged population, many states have passed legislation to ensure patients are informed of the condition and that they may benefit from supplemental screenings. Understandably, this has caused increased demand for safer, more effective forms of breast cancer detection techniques.

Researchers from the Mayo Clinic in Rochester, Minn., set out to determine if using molecular breast imaging (MBI) to detect cancer in mammographically dense tissue was still effective when patients’ exposure to radiation was significantly reduced.

To do so, lead author Deborah J. Rhodes, MD, and her colleagues at the Mayo Clinic performed both screening mammography and adjunct MBI studies on 1,582 women who had complete reference standards and met certain eligibility requirements from May 2009 to March 2012. Patients were administered 300 MBq of 99mTcsestamibi prior to undergoing MBI, less than half the conventional dose.

The results showed that low-dose MBI increased the rate of cancer detection per 1,000 screened from 3.2 for stand-alone mammography to 12 for the combination of mammography and MBI, resulting in a supplemental yield of 8.8. The team also saw increased sensitivity with adjunct MBI, rising from 24 percent with mammography alone to 91 percent with the combination of screening techniques.

MBI was particularly effective at detecting invasive cancers, with a success rate of 81 percent compared to 19 percent for mammography alone. Of those invasive cancers discovered by MBI only, 82 percent were node negative, suggesting the method could be a valuable asset in early cancer detection.

One drawback of the study was a heightened risk of false positives and unnecessary biopsy procedures resulting from MBI, which raised the recall rate from mammography alone by 6 percent.

The authors concluded that the use of MBI in supplemental screenings shows promise for the future of breast cancer detection. “We hypothesize that a screening program of biennial MBI alternating with biennial mammography in women with dense breasts would exploit what mammography finds and find what mammography misses, preserving the cancer detection rate found in this study without the additional costs and false-positive findings associated with supplemental screening.”