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MRI Is Better for Early Breast Cancer Detection | Lancet study August 14, 2007

Posted by ramunas in breast cancer, cancer genetics, research, technology.
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Last week issue of medical journal the Lancet presents an important data from 5-years perspective study, which shows that MRI (magnetic resonance imaging) outperforms conventional mammography for detection of ductal carcinoma in situ (DCIS), an early pre-invasive breast cancer which arises in the milk ducts (listen to the audio podcast stream from Lancet).

“MRI is more powerful and accurate for diagnosing pre-invasive breast cancer called ductal carcinoma in situ (DCIS),” concluded lead research Dr. Christiane Kuhl, from the Department of Radiology at the University of Bonn, Germany [via].

In the study, Kuhl and colleagues collected data on more than 7,300 women over five years. In addition to mammograms, the women were also given MRIs. The researchers wanted to see if MRIs could detect DCIS. The study found that x-ray based mammograms detect only 56% of early lesions in high risk women compared with 92% when magnetic resonance imaging scans (MRI) are used.

Moreover, of the 89 women diagnosed with “high grade” DCIS — the ones most likely to develop into cancer — 98 percent were found by MRI, compared with 52 percent found by mammography. In addition, 48 percent were missed by mammography but found by MRI alone (via).

Age, menopausal status, personal or family history of breast cancer or of benign breast disease, and breast density of women with MRI-only diagnosed DCIS did not differ significantly from those of women with mammography-diagnosed DCIS, study abstract states.

Cancer screening programmes are failing to detect nearly half of the earliest cases of breast cancer according to research which suggests women’s lives could be saved if all were offered hi-tech MRI scans, the Guardian states.

“If you picked up all cases of ductal carcinoma in situ [DCIS] you would prevent virtually all cases of breast cancer. Our finding that MRI is superior to mammography in detecting it turns things upside down.”, researchers said.

High-grade DCIS almost always becomes invasive and does so after a short time, Kuhl explained. “When it becomes invasive, it is biologically aggressive — that means it kills,” she said.

In contrast, low-grade DCIS usually remains within the duct and poses no threat. In fact, women can have low-grade DCIS for a lifetime with no ill effects, Kuhl said.

Also, MRI was not associated with many false positive findings. The positive predictive value of both methods was similar — 55 percent for mammography and 59 percent for MRI, the researchers reported.

“These findings can only lead to the conclusion that MRI outperforms mammography in tumour detection and diagnosis. MRI should thus no longer be regarded as an adjunct to mammography but as a distinct method to detect breast cancer in its earliest stage.”, said experts from the Radboud University Nijmegen Medical Centre in the Netherlands.

However, despite the technology’s advantages, its cost and a lack of people skilled at reading breast MRIs means it won’t replace mammograms any time soon, experts say.

“Also, MRI is more difficult to read, and you have to use different criteria to diagnose DCIS than for invasive breast cancer.” Since MRI is used less often than mammography “the number of radiologists who are experienced in interpreting breast MRIs is far smaller than the number of radiologists who are able to accurately interpret a mammogram”.

This is the beginning of the death of mammography, but that is going to be a long death,” Kuhl predicted. (via).

The study raises new questions about the national breast cancer screening programmes, which sees all women between the ages of 50 and 70 called in for regular mammograms but not MRI scans (at two-yearly visits in my country.) Only younger women at high risk of breast cancer are offered the more expensive MRI scans, because mammography is not informative in premenopausal women due to dense breast tissue.

Anyway, the results should be interpreted with caution (ref.):

“This study says that potentially mammograms are missing half of women with DCIS. The implication is that mammograms may not be the most sensitive way of finding early breast cancer, but it is clearly saying that more research is needed. A lot of women walk around with it without it being invasive or harmful. Some clinicians argue that we are over-diagnosing and over-treating already. It doesn’t seem practical to do MRI on every woman. It’s costly and very time-consuming as well”, says consultant nurse at Breast Cancer Care.

“The programme uses mammography to screen all women in the UK aged 50 or more for breast cancer. The results in the Lancet are not representative of the screening population, and so have to be interpreted with care”, states Julietta Patnick, director of UK NHS cancer screening programmes.

Senior policy officer at Breakthrough Breast Cancer, said: “This is an interesting but complex study which gives us more information about the detection of early breast changes. However, it is important to note that the women who took part in this study had a higher chance of an abnormality being found and therefore are not representative of the general population.”

What is a connection between MRI, DCIS and cancer genetics, you may wonder? It is now well established, that BRCA1-positive breast tissue has different histopathological appearance and course – its usually G3, estrogen negative and expressing basal-like phenotype. Recently published studies from Canada, Italy, Germany (btw, by the same author), the Netherlands and UK (MARIBS study) all similarly showed, that MRI outperforms mammography in BRCA1 breast cancers and annual MRI is now included as addition to mammography for TP53, BRCA1 and BRCA2 mutation carriers screening programs, performed from 30 till 49 years in UK and other countries. Cost effectiveness of MRI is also proven.

MRI procedure is more invasive than mammography, because contrast enhancing substance must be injected intravenously and special equipment is used:

The genetics of DCIS is also interesting topic – it is only several years since it was shown, that DCIS cases actually have the same proportion of BRCA1 and BCRA2 mutation as invasive breast cancer has – mutations were found in a significant proportion of women with DCIS who presented for hereditary risk assessment [via]. DCIS is equally as prevalent in patients who carry deleterious BRCA mutations as in high familial-risk women who are non-carriers, but occurs at an earlier age [via].

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1. pulasthi - August 14, 2007

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