MRI finds breast cancer before it becomes dangerous

A study in the Lancet (vol. 370, 11 August 2007) could lead to a change of paradigm in the early diagnosis of breast cancer. It states that magnetic resonance imaging (MRI) is substantially more accurate than mammography in diagnosing very early stages of breast cancer . Up to now MRI was thought to be hardly suited for the detection of such 'ductal carcinoma in situ (DCIS) . Researchers at the University of Bonn have now come to a completely different conclusion. In the past five years they examined more than 7000 women with both methods. In a total of 167 women the doctors found early forms of breast cancer – 152 (92 %) of these were found using MRT, 93 (56 %) with mammography.

Breast cancer forms in the cells which line the inside walls of the milk ducts. The tumour initially remains in the milk duct and is therefor called " intraductal cancer" or DCIS (ductal carcinoma in situ).

Although even at this stage it is called a carcinoma, it behaves actually like a benign disease, which can always be treated successfully by operating on it. Only when the tumour grows out of the milk ducts into the breast’s glandular tissue can it spread via blood and lymph vessels in the body. 'If we find DCIS and remove it we can prevent the formation of “real” breast cancer,' the Bonn radiologist Professor Christiane Kuhl explains. 'That way we prevent the development of a disease that is often life-threatening.'

However, there are different forms of intraductal carcinomas: the less aggressive (low-grade) and highly aggressive (high-grade) DCIS. Whereas low-grade DCIS is relatively inert and may never spread beyond the milk duct (and thus may never pose a threat to the women affected), high-grade DCIS will virtually always break out of the milk ducts, and then will become dangerous, biologically aggressive high grade invasive breast cancer. This makes it all the more important to discover such high-grade DCIS.

Until To date mammography was the 'gold standard' of breast cancer medicine

It has been known for a long time that MRI is superior to mammography as far as the diagnosis of invasive breast cancer is concerned. However, the search for DCIS to date has been the preserve of mammography. It highlights small calcifications which form in the milk ducts affected. On the MRI scan, depositions of this kind are invisible. Therefore MRI was hitherto seen as unsuited for detecting intraductal carcinoma, which was one of the main reasons for only using mammography for the early detection of breast cancer.

With their results the Bonn researchers confounded this textbook wisdom. A total of 7319 women were investigated by Professor Kuhl and her colleagues in the last five years using both methods. In 167 of them they found early stages of breast cancer. 'Using mammography only 93 cases of DCIS could be seen, compared with 153 cases detected by MRT,' is how Professor Kuhl sums up the results. 'And not only that: it was above all the particularly aggressive high-grade DCIS which were especially reliably picked up using MRI, but especially difficult to detect using mammography.'