EH 2_2015

Integrated drug pump! Wireless & 3-Tesla-capable! Innovation – Made in Germany! STRESScan be so relaxing. The specialist for Stress-MRI! Contrast medium injectors and consumables for CT, MRI and angiography Hauptstr. 255 D-66128 Saarbruecken www.medtron.com Accutron® MR3! EuropHopital15_Druck.qxp_Layout 1 17.04.15 10:39 Seite 1 EUROPEAN HOSPITAL Vol 24 Issue 2/15 22 RADIOLOGY Breast cancer screening AB-MRI could be the ideal screening tool Report: Mélisande Rouger ‘If one thing has been proven by screening mammography, it is that early diagnosis of a malignant dis- ease does indeed translate into improved survival. This concept justifies the use of screening in general and specifically for breast cancer. We have indeed seen a decrease of mortality rates over the past decades,’ said radiologist Professor Christiane Kuhl, opening her presentation during a Satellite Symposium at this year’s ECR. However, regardless of the ben- efits, a number of issues still call for improved cancer screening meth- ods. Mammographic screening, just like PSA screening for prostate can- cer, may pick possibly irrelevant diseases, which even if left undiag- nosed would never progress to an actual life-threatening condition. Early publications on over- diagnosis through mammographic screening claimed that one out of three breast cancers represented over-diagnosis. However, it is cur- rently, and probably more realisti- cally, estimated that about 10% of breast cancers do belong to that group, Kuhl pointed out. Mammography in fact has tech- nology-inherent bias to detect slow- ly growing cancers. ‘What we really pick are calcifications and architec- tural distortions. So triple negative breast cancers, which grow rapidly and don’t calcify, are likely to go unnoticed by mammography,’ she explained. The detection of breast cancer through mammography depicts pathophysiological changes that reflect regressive changes such as hypoxia, necrosis, fibrosis, calcifi- cation and architectural distortions. Another challenge with mam- mography is under-diagnosis. ‘Surprisingly enough, this is not discussed so much by the scien- tific community, although it’s clear that mammography screening has a limited sensitivity for prognostically relevant disease,’ she pointed out. Despite decades of studying breast cancer in epidemiologic studies, it continues to be the leading cause of cancer death in women and the most common cause of death in women under 50. ‘Over-diagnosis is not our main problem. If it were, no one would die. Both over and under-diagnosis are shortcomings of mammographic screenings,’ she said. Other screening candidates have been studied, starting with digi- tal breast tomosynthesis (DBT). A study that was conducted in over 400,000 women and published last year in JAMA showed that DBT presented with a 30% increase in detection rate compared with mam- mography alone. Another side effect was an improved PPV, in other words a higher specificity in distin- guishing pathology alterations and benign changes. In 2008 another study, also pub- lished in JAMA, compared the use of hand-held ultrasound with mam- mography and found an additional cancer yield of 4.1 per thousand. Acquisition time, on the other hand, was considerable, as it took over 20 minutes to complete a bilat- eral screening examination. Two years later, the authors published an update, in which they compared a single round of screening MRI with mammography. They found a 14.6 per thousand additional cancer yields with MRI. Kuhl is a strong advocate for MRI in breast cancer screening. Fifteen years ago, she and her team pub- lished the very first paper on the topic, in which they highlighted MRI’s high sensitivity and specific- ity. Their updated results, in 2005 and 2010, reported the exact same data. Moreover, the EVA trial, which was conducted in four different sites in Germany, confirmed that MRI had higher sensitivity than ultra- sound or mammography in women at increased risk of breast cancer. Interestingly, other publications that reported lower sensitivity of MRI compared with mammography found opposite results a few years later, stressing the importance of the user’s experience with MRI, Kuhl explained. ‘This evolution curve is represented in many studies. If you see variable results for MRI for screening use, this usually reflects a learning curve that radiology or the radiological community has to take in every area, not only for breast MRI but also possibly for prostate MRI.’ Kuhl also set out to tackle critics about MRI’s supposedly high false positive rates in her presentation. ‘MRI has often been reported to offer low specificity, which is cer- tainly not true. Again, that is some- thing that can be avoided with expe- rience. More recent multi-centre tri- als, such as the EVA trial, showed that MRI had higher specificity than mammography,’ she confirmed. MRI can also be used as a screen- ing tool for women at average risk. In an upcoming paper, Kuhl will show that, in those women, MRI has a 20 per thousand detection rate and an acceptably high PPV. Finding more cancers with MRI should not be a problem, the researcher believes: ‘More diagnosis is not more over-diagnosis, because, even today, too many women die of breast cancer. We still have a prob- lem. We don´t have to detect all the cancers but we should detect the ones that kill.’ The main issue facing MRI today is that economic considerations are driving its use for screening. One reason for high costs is the fact that the same (extensive) pulse sequence protocols have been used for breast MRI screening as the ones that have been used for diagnostic purposes. To make breast MRI a real screen- ing tool, Kuhl introduced the con- cept of abbreviated breast MRI (AB-MRI). ‘AB-MRI means to strip down the pulse sequence protocol to its very essence,’ she explained. Her corresponding study (pub: Journal of Clinical Oncology, 2014) used such an abbreviated proto- col, which consisted of one pre- and one post-contrast acquisition, equaling a magnet time of about three minutes. Conducted between 2009 and 2010, the study compared the diagnostic accuracy and can- cer yield of this abbreviated pro- tocol against that full breast imag- ing protocol. Kuhl found that this was sufficient to help diagnose the same number of additional cancers, with similar diagnostic accuracy. Moreover, she found that the radi- ologists reading time of just three seconds was enough to exclude the presence of breast cancer with a negative predictive value of just under 99%. ‘Establishing absence of breast cancer on a negative MIP image is done in the blink of an eye,’ she said, ‘and, in a screening setting, the vast majority of women have no cancer. By comparison, for a negative screening ultrasound study, a radiologist needs to work for 20 minutes.’ Accordingly, AB-MRI actually has the potential to make breast MRI a real screening tool, she argued. ‘AB-MRI offers an additional can- cer yield of 18.3 per thousand in women who have been pre- screened by digital full-field mam- mography and physician-performed breast ultrasound. It may be the ideal screening tool for women because it is conceivable to conduct on a population-wide scale, has high sensitivity for biologically rel- evant cancers and high diagnostic accuracy – and there’s no radiation involved.” Kuhl pointed out that, just like prostate MRI, breast MRI is relative- ly blind for low-grade disease, espe- cially low-grade DCIS. ‘Replacing mammography by breast MRI, rath- er than adding MRI to mammogra- phy, may therefore be the way to proceed,’ she said. Radiologists must understand that the aim of breast cancer screening is not to detect all breast cancers and their precursors by all means, she insisted. ‘Rather, the goal must be to develop imaging methods that combine a maximum sensitivity for prognostically relevant disease with a desirable lack of sensitivity for disease that is prognostically unimportant.’ MRI is increasingly relevant to cancer management, especially to detect breast carcinoma. Professor Christiane K Kuhl from the department of diagnostic and interventional radiology at the University of Aachen, Germany, strongly advocated in favour of MRI in breast cancer screening during a dedicated Satellite Symposium organised by Bracco at ECR 2015 Christiane K Kuhl is a professor in the diagnostic and interventional radiology department at the University of Aachen, Germany Patient with a small carcinoma in the right breast that is only visible in the MRI image (right). In the MIP image (left) it cannot be seen EuropHopital15_Druck.qxp_Layout 117.04.1510:39 Seite 1

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