MRI Detects Breast Cancer Missed by Mammography

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March 29, 2007 — At the time when cancer is diagnosed in one breast, magnetic resonance imaging (MRI) can detect cancer in the other breast that has been missed by mammography and clinical examination, which is the current practice standard.

These findings come from a study involving 969 women, and MRI detected cancer in 30 of the women, giving an additional diagnostic yield of 3.1%. The results are reported in the March 29 issue of The New England Journal of Medicine.

"Our study shows that MRI can improve the detection of cancer in the contralateral breast when added to a thorough breast examination and mammographic evaluation at the time of the initial diagnosis of cancer," write the authors. Led by Constance D. Lehman, MD, PhD, from the University of Washington in Seattle, the researchers represent the American College of Radiology Imaging Network (ACRIN) Trial 6667 Investigators Group, a co-operative group sponsored by the National Cancer Institute (NCI).

"The current cost of MRI precludes its widespread use in general population, but this imaging tool appears to increase the detection of cancer in women at increased risk, such as women with a recent diagnosis of breast cancer," the authors comment.

"One in ten women diagnosed with cancer in one breast will develop the disease in the opposite breast. Having a better technique to find these cancers as early as possible will increase the chances of successful treatment," the National Institutes of Health director Elias Zerhouni, MD, stated in a press release.

Increasing Use in Breast MRI
"A growing number of patients with newly diagnosed breast cancer are undergoing further evaluation with MRI," Robert Smith, PhD, from the American Cancer Society, notes in an accompanying editorial. These latest findings will likely lead to an increase in MRI screening for such patients, and also to debate over whether it should become standard practice, Dr. Smith said in an interview.

There is, in general, an increasing use of MRI for breast cancer screening, Dr. Smith said, and this study, and similar research, is likely to increase it further. However, there are concerns over the quality of MRI that is available, and in particular, concern that some centers performing MRI do not have the facility to also perform biopsies. In his editorial, Dr. Smith comments, "It is unclear whether the results reported by Lehman and colleagues could be reproduced in all centers offering MRI today."

There are also issues with access. MRI is not available in every clinical setting, and "there are almost certainly discretionary decisions being made about when to use it and when not to use it that would benefit from more guidelines," Dr. Smith commented to Medscape. He says there is a need for additional research — some of which is already underway — that will lead, over time, to greater clarity in the recommendations for when MRI should be carried out.

Accuracy Better Than in Previous Studies
Dr. Lehman and colleagues report an overall high accuracy for MRI, with better results than have been reported previously in smaller studies.

The specificity for MRI in the contralateral breast was 91%, and the specificity was 88%. MRI detected an abnormality in 121 (12.5%) of the 969 women who participated in the trial, all of whom underwent a biopsy. Of these 121 biopsies, 30 specimens had positive results indicating cancer (24.8%).

Among the 30 cancers identified, 18 were invasive tumors, with a mean diameter of 10.9 mm (range, 1 - 42 mm). The remaining 12 specimens were ductal carcinomas in-situ. "Recent studies provide support for the benefit of detecting DCIS [ductal carcinomas in-situ], since this tumor is likely to progress to invasive disease if left untreated," the researchers comment. Nearly all of the cancers detected were early stage (0 or 1, only 1 was stage 2), and all of those examined (27/30 women) had clear lymph nodes.

The cancers identified on MRI are in general at an earlier stage than those identified on other types of examinations, the researchers commented in a press release. This is important because breast cancers detected at an earlier stage are often more treatable, they add.

The negative predictive value of MRI in the population studied was "extremely high (99%)," Dr. Lehman and colleagues report. The risk for an occult cancer is the contralateral breast 1 year after negative MRI results was estimated at 0.3%. This information may be helpful to women and their clinicians in discussing the relative value of bilateral mastectomy after cancer has been diagnosed in one breast, they comment.

"This study gives us a clearer indication that if an MRI of the opposite breast is negative, women diagnosed with cancer in only one breast can more confidently opt against having a double, or bilateral, mastectomy," commented NCI director, John Neiderhuber, MD. "Although no imaging tool is perfect, if the MRI is negative, the chance of cancer in that breast is extremely low. A potential outcome that we would be delighted to see is fewer unnecessary bilateral mastectomies," Dr. Lehman added.

Women With Recent Breast Cancer Diagnosis
"I do think that these results support the benefit of MRI in evaluating women with a recent breast diagnosis," Dr. Lehman commented to Medscape. Adding MRI to mammography provides clinicians with a more extensive evaluation of the breast, providing more information on which to base decisions about treatment and surgery.

However, at present, there is no official recommendation. There are guidelines for the use of MRI for breast screening, and an updated version from the American Cancer Society has been published (CA Cancer J Clin. 2007;57(2):90-104) to coincide with The New England Journal of Medicine article. However, these guidelines cover the use of MRI screening for breast cancer in asymptomatic women, Dr. Smith pointed out to Medscape, and not in patients who already have a diagnosis of breast cancer, such as the ones in the Lehman study.

In addition to problems with access to MRI, and concerns over the quality of the MRI that is performed, there are issues with reimbursement for the procedure. In the United States, some insurance companies provide reimbursement for breast MRI imaging, but others do not. The American College of Radiology is working to help standardize reimbursement. One of the problems is cost, as MRI scans can vary from $800 to $2000 compared with $85 to $150 for a mammogram.

However, an investment in breast MRI could reduce the eventual cost of treatment, the researchers argue. Earlier detection could lead to one surgery instead of 2 or result in fewer rounds of chemotherapy. Dr. Lehman and colleagues are now conducting cost analyses to determine whether MRI, at the time of initial diagnosis, will provide savings because of more targeted, efficient, and effective treatment.

N Engl J Med. 2007;356:1295-1303, 1362-1364.

Source: http://www.medscape.com/viewarticle/554290?src=mp