A new breast imaging technique pioneered at Mayo Clinic nearly quadruples detection rates of invasive breast cancers in women with dense breast tissue according to results of a recent major study. Molecular Breast Imaging (MBI) is a supplemental imaging technology designed to find tumours that would otherwise be obscured by surrounding dense breast tissue on a mammogram. Tumours and dense breast tissue can both appear white on a mammogram, making tumours indistinguishable from background tissue in women with dense breasts. About half of all screening-aged women have dense breast tissue, according to Dr Deborah Rhodes, a Mayo Clinic Breast Clinic physician and the senior author of this study.
MBI increased the detection rate of invasive breast cancers by more than 360% when used in addition to regular screening mammography, according to the study. MBI uses small, semiconductor-based gamma cameras to image the breast following injection of a radiotracer that tumours absorb avidly. Unlike conventional breast imaging techniques, such as mammography and ultrasound, MBI exploits the different behaviour of tumours relative to background tissue, producing a functional image of the breast that can detect tumours not seen on mammography.
The study, conducted at Mayo Clinic, included 1,585 women with heterogeneously or extremely dense breasts who underwent an MBI exam at the time of their screening mammogram. Of these women, 21 were diagnosed with cancer – five through mammography alone (24% or 3.2 cancers per 1,000 women) and 19 with mammography plus MBI (91% or 12 cancers per 1,000 women). Particularly notable was the four-fold increase in detection of invasive cancers (1.9 invasive cancers per 1,000 women with mammography and 8.8 per 1,000 women with mammography plus MBI). Detection rates for non-invasive cancers were not significantly different.
The risk of incurring an unnecessary biopsy because of a false positive exam increased in this study, from 1 in 100 women with mammography to 4 in 100 women with mammography plus MBI. (By comparison, recent studies have shown that alternative supplemental screening techniques, such as ultrasound and MRI, generate about eight additional unnecessary biopsies per 100 women.)
"These findings suggest that MBI has a more favorable balance of additional invasive cancers detected versus additional biopsies incurred relative to other supplemental screening options," says Rhodes. "Recent studies have reported supplemental cancer detection rates of 1.9 per 1,000 women screened with automated whole breast ultrasound and 1.2 to 2.8 per 1,000 women screened with digital breast tomosynthesis, so our finding of an additional 8.8 cancers per 1,000 women makes MBI a very compelling option for women who elect supplemental screening,£ says Rhodes.
Dr Michael O’Connor, a Mayo Clinic scientist and inventor of the MBI technology, calls this latest study a major milestone for both safety and efficacy of the imaging device, largely because of the high detection rates achieved through low radiation exposure. "This new study is important because it incorporates many of the advances in MBI pioneered here at Mayo Clinic and shows that studies can be performed safely, with low radiation exposure to the patient," says O’Connor. "This means MBI is safe and effective as a supplemental screening tool."
[link url="http://newsnetwork.mayoclinic.org/discussion/new-breast-exam-nearly-quadruples-detection-of-invasive-breast-cancers-in-women-with-dense-breast-ti/"]Mayo Clinic release[/link]
[link url="http://www.ajronline.org/doi/abs/10.2214/AJR.14.13357"]American Journal of Roentgenology abstract[/link]