MRI and Ultrasound Gain Ground in Breast Imaging
The journey from bench to bedside is a long one in medicine, but breast MRI received a boost in March 2007 when the American Cancer Society (ACS) revised its guidelines for breast cancer screening to include annual MRI for high-risk women, a group representing about 2 percent of the US population. That same month, a report1 on the ACR Imaging Network 6667 trial was published in the New England Journal of Medicine, recommending contralateral breast MRI for women recently diagnosed with breast cancer. In addition, the ACS recommends that women with extremely dense breasts, a personal history of breast cancer, and atypical hyperplasia receive breast MRI at their physicians’ discretion.
Another adjunct breast-imaging modality is poised to assume an even greater role in breast cancer screening and diagnosis. Ultrasound, long used to help evaluate suspicious lesions and cysts and to guide breast biopsies, has been generating a growing list of scientific citations since emerging as a hot topic at the 2006 meeting of the European Congress of Radiology (ECR) for a different reason: elastography.
Numerous studies have indicated that elastography, which uses ultrasound waves to measure the elasticity of tissue, could be a useful diagnostic tool for several cancers, including breast malignancies. Cancerous tissue is less pliant than regular breast tissue; according to the results of one British study presented at ECR 2006,2 the sensitivity and specificity of breast elastography are 96 percent and 53 percent, respectively, meaning that the technique could be used to determine whether a lesion is benign or malignant without invasive biopsy. Later that year, a poster presentation3 at the annual RSNA meeting showed similar results.
An article4 published in the July 2008 issue of Breast Cancer, “Cost-effective Screening for Breast Cancer Worldwide: Current State and Future Directions,” provided another argument for the use of elastography in breast cancer diagnosis: its affordability. “Clinical results demonstrate that elasticity imaging, even in its simplest and least sophisticated versions, like tactile imaging, has significant diagnostic potential comparable and exceeding that of conventional imaging techniques,”4 the study’s authors wrote. “Tactile imaging is one method that has the potential to provide cost-effective breast cancer screening and diagnostics.”4
A National Cancer Institute clinical trial to validate the use of elastography in breast cancer evaluation was launched in July of 2008 and is currently recruiting participants.
Meanwhile, ultrasound guidance for breast biopsy and surgery continues to gain momentum. A recent study5 published in Breast looks at the use of vacuum-assisted, ultrasound-guided breast biopsy for difficult indications, including lesions with scarring or distortion, and small tumors or microcalcifications. The study indicates that the technique helped patients avoid difficult surgery in 41 of 51 cases. Another study,6 published in the August 2009 issue of the American Journal of Surgery, looks at using an ultrasound-guided electrosurgical loop to excise breast lesions, noting that the technique shortened procedure times and allowed incisions to be smaller.
As breast MRI proliferates around the country following the 2007 ACS revisions to its screening guidelines, research into the diagnostic potential of the modality for breast cancer continues apace. The ACS recommendation came with a caveat: The relatively low specificity of MRI could lead to false positives, resulting in unnecessary biopsies. Some hope computer-aided detection could be a solution. A study7 published online in September 2009 in European Radiology evaluated the accuracy of a computer-aided detection program against manual interpretation by radiologists, finding that interpretation based on computer-aided detection had a specificity of 86.4 percent. Without computer-aided detection, the specificity of MRI was found to be around 69 percent.
Another European Radiology study8 published online in September 2009 looks at the use of MR elastography (MRE), an experimental technique that uses MRI instead of ultrasound to look at tissue elasticity. According to the results of the study, the addition of MRE to conventional MRI of the breast resulted in sensitivity approaching 98 percent, leading the study’s authors to conclude the combination of MRE and contrast-enhanced MRI could increase the diagnostic performance of breast MRI.
References
1. Lehman CD, Gatsonis C, Kuhl CK, et al. MRI evaluation of the contralateral breast in women with recently diagnosed breast cancer. N Engl J Med. 2007;356(13):1295-1303.
2. Proceedings of the European Congress of Radiology. ECR: Vienna, Austria; 2006.
3. Thomas A, Fischer T. An advanced method of ultrasound: realtime elastography—first experience in 300 patients with breast lesions. Poster presented at: 92nd Scientific Assembly and Annual Meeting of the Radiological Society of North America; November 26–December 1, 2006; Chicago, IL.
4. Sarvazyan A, Egorov V, Son JS, Kaufman CS. Cost-effective screening for breast cancer worldwide: current state and future directions. Breast Cancer: Basic and Clinical Research. 2008;1:91-99.
5. Abbate F, Bacigalupo L, Latronico A, et al. Ultrasound-guided vacuum assisted breast biopsy in the assessment of C3 breast lesions by ultrasound-guided fine needle aspiration cytology: results and costs in comparison with surgery. Breast. 2009;18(2):73-77.
6. Fine RE, Schwalke MA, Pellicane JV, Attai DJ. A novel ultrasound-guided electrosurgical loop device for intra-operative excision of breast lesions: an improvement in surgical technique. Am J Surg. 2009;198(2):283-286.
7. Meeuwis C, van de Ven SM, Stapper G, et al. Computer-aided detection (CAD) for breast MRI: evaluation of efficacy at 3.0 T [published online ahead of print September 2, 2009]. Eur Radiol.
8. Siegmann KC, Xydeas T, Sinkus R, Kraemer B, Vogel U, Claussen CD . Diagnostic value of MR elastography in addition to contrast-enhanced MR imaging of the breast—initial clinical results [published online ahead of print September 1, 2009]. Eur Radiol.
ACS Breast MRI Recommendations
The American Cancer Society (ACS) recommends1 an annual MRI exam for women who have the following indications:
• the BRCA1 or BRCA2 genetic mutations, or a first-degree relative with either;
• a lifetime risk for breast cancer that has been scored at 20 percent or higher;
• receipt of chest radiation between the ages of 10 and 30; and
• Li–Fraumeni syndrome, Cowden syndrome, Bannayan–Riley–Ruvalcaba syndrome, or a first-degree relative with any of these.
The ACS acknowledges that while data are insufficient to make a recommendation either for or against screening with MRI in the following risk subgroups, physicians should make individualized decisions on whether women with the following risk factors receive breast MRI exams:
• a personal history of breast cancer,
• carcinoma in situ,
• atypical hyperplasia, and
• extremely dense breasts on mammography.
Reference
1. American Cancer Society Guidelines for breast screening with MRI as an adjunct to mammography. CA Cancer J Clin. 2007;57:75-89.
Tags: Breast Imaging, MRI, Ultrasound
Category: Medical Imaging —