The benefits of mammography for breast cancer screening have been discussed for years. By screening, some say that tumors are discovered earlier, save lives and eliminate the need of having to go through strenuous therapies. Others say that screening often leads to over diagnosis and an excess of therapy in addition to a great level of x-ray radiation exposure.
Factual and undisputed is: The accuracy of mammography is not so good that it does not require any improvement. A “source of hope” for this includes phase-contrast imaging, a procedure based on x-rays which is of special interest for breast cancer diagnosis, and has wider applications.
As the largest medical trade fair with around 4,500 exhibitors, this year’s MEDICA, World Forum for Medicine (November 12 – 15 in Düsseldorf, Germany) offers insight into new diagnostic procedures involving both imaging and molecular biological procedures. The mammography screening program which had been established in Germany over 10 years ago has been increasingly questioned. A reason for doubting the benefit of the screening program entails more and more studies showing that the benefit-risk ratio of screening may be unfavorable. The basic criticism is that the rate of superfluous diagnoses and therapies is too low in relation to the reduction of breast cancer mortality. The basic known problem of breast cancer screening is more preliminary stages of cancer (in situ carcinomas) are being recognized, whose development of an invasive carcinoma, however, cannot be assessed confidently enough.
In this connection, authors of a Canadian study published this year did identify a reduction of 21 percent in cancer mortality over the course of 25 years, but also determined the rate of over diagnosis to be 21 percent. In addition, a data analysis from the U.S. increases doubt concerning the benefits of screening. In the case of 1,000 women subjected to a mammography on an annual basis, 0.3 to 3.2 breast-cancer related deaths are prevented. There is however, a price to be paid: In the case of 490 to 670 women, there is at least one false alarm, for which three to 14 women ended up being subjected to over diagnosis and useless therapy.
An analysis of the Swiss “Health Technology Assessment Committee” did not portray mammography screening in a good light. Of course, these current analyses are everything but undisputed, particularly as a multitude of other studies have resulted in a positive benefit-risk ratio. Therefore, discussion about the benefit of mammography screen programs will continue for a long time.
Phase-contrast x-ray imaging, a ‘source of hope’
There is broad consensus that mammography requires improvement. This is because, despite significantly improved image quality by introducing full-field digital mammography, the 62 to 88 percent detection rate of malignant focal lesions is still relatively low. In particular, in the case of young women with dense mammary gland tissue as well as women at higher risk due to family anamnesis, digital mammography reaches its limits, explained Dr. Susanne Grandl and her colleagues from the Institute for Clinical Radiology at the Hospital of the Ludwig Maximilians University of Munich (Germany).
According to the radiologist, phase-contrast imaging is deemed to be significant progress. This relatively new technique provides very sharp, detailed and high-contrast images, showing structures that would be blurred or not recognized at all using conventional mammography. The technical and physical reason for the superior image quality is that Phase-contrast x-ray imaging does not only measure the breast (mammography, tomosynthesis and computer tomography) as to how much the tissue absorbs the x-ray radiation as is the case with conventional x-ray imaging, but a measurement is also taken on “how the tissue laterally deflects the radiation and how it affects the peak-to-valley oscillation of the radiation wave – the so-called phase.
Among others, scientist around Marco Stampanoni, Professor at the Institute for Biomedical Technology at ETH Zürich university (Switzerland) have demonstrated what is possible using phase-contrast x-ray imaging technology: With the new technology, researchers were able to generate mammograms which are capable of diagnosing breast cancer and its preliminary stages more precisely than up to now. The hope of the scientists is that the new procedure could contribute to utilizing biopsies in a very concise manner and improve follow-up examinations.
“In comparison to conventional mammography, we hope that the method will better show where a biopsy has to be made within the breast tissue,” said Professor Rahel Kubik, Head Radiologist at the Baden Cantonal Hospital. But, she also mentioned that the method has to still be evaluated against a large number of cases. “However, we are confident of the fact that the findings of the new method will allow us to classify the various known microscopic calcification types,” affirmed Professor Gad Singer, Head Physician at the Institute for Pathology of the Baden Cantonal Hospital.
Improved tumor diagnosis, but…
In the meantime, according to Dr. Grandl and her colleagues, several studies have shown that breast cancer diagnosis can be improved using various phase-contrast imaging techniques. In this way, microstructures, collagen strands and microcalcifications could be depicted with improved sensitivity. Additionally, the phase-contrast CT provides “3D image data in high resolution in a way that was only possible within the scope of histology.” And within the scope of in vivo studies, “phase-contrast mammography has resulted in a gain in sensitivity and specificity in the case of primarily unclear diagnosis”. However, it is a totally different question if whether this technique can be used for breast cancer screening in the future: According to the radiologists from Munich (Germany), “the only study on phase-contrast mammography in the screening setting for phase-contrast mammography up to this point has not resulted in any significant advantages regarding sensitivity and recall rate.” However, the new technology could “possibly be used as an additional option in unclear cases of diagnosis in select subgroups, for example in the case of women with dense breast tissue.” And phase-contrast CT provides additional “information when examining ex vivo samples” and could “possibly improve the diagnosis of excised material.”
Phase-contrast imaging is not only limited to breast cancer diagnosis. Breast cancer is only one of many diseases phase-contrast x-ray imaging is currently being researched for. Using this technology, in the future, not only tumors should be better detected and, in particular, be identified earlier but also vasoconstriction, atherosclerosis and arthrosis for example.
Possible fields of application include tumor staging in the case of oesophagus carcinoma using phase-contrast CT; diagnosis in the case of focal liver lesions; and in the case of lung diseases. For the first time, scientists at the Helmholtz Center in Munich, the University Hospital of Munich and the Technical University of Munich have recently tested phase-contrast radiography in vivo for the diagnosis of lung diseases. As the team has reported, the method already assures the detection of diseases such as pulmonary emphysema early on. Further studies should now test how the new technology can be used in the clinical field, for the diagnosis of pulmonary emphysema or lung fibrosis for example.
Exhibitors at MEDICA 2014 showing innovations in the field of medical imaging (e.g. x-ray imaging/ computer tomography, magnetic resonance tomography, ultrasound) are now online in the Company & Product category at http://www.medica-tradefair.com. New and approved approaches to oncological diagnosis and therapy will be examined and discussed in detail at the accompanying MEDICA EDUCATION CONFERENCE. For information on the current program of the conference visit http://www.medica.de/mec1.
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