Role Found for MRI in Newly Diagnosed Breast Cancer

CHICAGO, May 21 -- Among women with newly diagnosed breast cancer, MRI of both breasts may be helpful in determining surgical treatment, researchers here suggested.

Preoperative breast MRI resulted in a beneficial change in surgical management in 9.7% of newly diagnosed breast cancers, said Kevin P. Bethke, M.D., of Northwestern University, and colleagues.

But, the false positive rate was almost 80%, they reported in the May issue of the Archives of Surgery.

In a retrospective analysis of a prospective database at an academic tertiary-care center, 155 women (mean age 53, range 34 to 75) with breast cancer newly diagnosed by mammography, ultrasonography, and needle biopsy underwent preoperative bilateral breast MRI. The study took place in a single-institution, single-surgeon setting from April 2005 through April 2006.

MRI found 124 additional suspicious lesions in 73 patients, the researchers reported. Follow-up mammograms or ultrasonograms were required for 65 patients and 41 patients underwent additional image-guided biopsies.

There was a change in surgical management as MRI discovered additional, otherwise undetected, malignancies in 36 patients (23.2%) on the basis of radiographic-pathologic correlation.

Lumpectomy was converted to mastectomy in 10 patients (for eight patients it was a beneficial change), wider excision was performed in 21 patients (10 beneficial), and five patients (two beneficial) underwent contralateral surgery.

Larger tumor size was an independent predictor of a beneficial change in surgical management (odds ratio, 1.66; 95% confidence interval, 1.04-2.66).

Seven patients had a suspicious lesion in the contralateral breast. Of these, two had a biopsy-proven malignancy and two with a biopsy specimen showing atypical ductal hyperplasia had lumpectomy. The remaining three patients chose not to have a needle biopsy of the lesion but to have a prophylactic mastectomy, the researchers reported.

The final pathologic report confirmed the two biopsy-proven malignancies, but not malignancy in the two patients with atypical hyperplasia or the three who chose mastectomy rather than an image guided biopsy.

Of the 36 patients (23%) for whom a surgeon determined that a change in management was merited, the change was found beneficial in 41.7% on radiographic-pathological confirmation, the researchers reported.

Overall, the researchers said, preoperative breast MRI resulted in a beneficial change in surgical management in 9.7% of newly diagnosed breast cancers. Thus, 10 women must undergo a breast MRI for one to have a beneficial change in management, they said.

Unfortunately, Dr. Bethke said, MRI had a considerable false-positive rate: 79% (58/73) of MRI-detected lesions were ultimately benign. Furthermore, the low rate of detection of a contralateral malignancy of 1.3% may be attributable to the routine use of mammography and ultrasonography before MRI at the study institution.

The cost of MRI technology has been a significant limitation and deterrent in the routine use of the technology, the researchers wrote.

Also, they said, some argue that MRI-detected lesions are not clinically relevant. Women having a lumpectomy, the argument goes, should receive post-operative radiation therapy, resulting in irradiation of any small ipsilateral lesions that may have been missed.

In addition, opponents of MRI in these situations argue that breast cancer patients would be aggressively screened so that a lesion in the contralateral breast missed by initial mammography would be detected early, the researchers said.

To such arguments, Dr. Bethke responded that if it is important to clear lumpectomy margins of microscopic disease to minimize the risk of local recurrence, it would follow that small foci detected on MRI also warrant identification and excision.

The 9.7% beneficial change in surgical management of these patients is likely to increase with time as MRI technology progresses, radiologists' experience improves, and the cost of MRI decreases, the researchers said. Thus, breast MRI may have a role in the staging evaluation of newly diagnosed breast cancers, they concluded.

In a discussion that took place at the annual meeting of the Western Surgical Association, November 13, 2006, in Los Cabos, Mexico, three physicians posed questions for Dr. Bethke.

Baiba J. Grube, M.D., of Yale, asked whether the study findings should be considered a contraindication to breast conservation without randomized prospective data on the impact on in-breast recurrence?

To this, Dr. Bethke replied that "almost everyone would agree that our goal is to surgically remove as much of the cancer as possible prior to radiation, using safe, efficient, and cost-effective methods. MRI is not yet at the level of usefulness we desire but will continue to evolve and improve."

Dr. Grube pointed out that "the purpose of the MRI evaluation is to change treatment for the few patients who are destined to have in-breast recurrence and require mastectomy at a later date. More than half of the women in this study underwent a change in surgical management that could be described as "unnecessary." The MRI data lead to two unnecessary ipsilateral mastectomies and three unnecessary contralateral prophylactic mastectomies based on MRI findings."

He wrote "this is a high price to pay for preventing a mastectomy at a later time for perhaps 5% of the breast conservation patients treated with current therapies.

Dr. Grube also asked whether the indications for preoperative MRI have changed as a result of this study. To this question, Dr. Bethke answered, "Yes." Our current indications, he said, "are to perform MRI on patients younger than 40 or on those with dense breasts. We will also obtain an MRI for women with invasive lobular cancer and those with occult disease manifested by nodal metastases in the absence of mammographic or sonographic abnormalities."

Alden H. Harken, M.D., of the University of California, San Francisco, asked whether there was something fundamental about the biology of breast cancer that would make it uniquely visible by any test, or "are you just adding more tests to increase sensitivity at the expense of specificity and cost?"

To this, Dr. Bethke replied, "We did this study because we were frustrated by the lack of guidelines for the use of breast MRI. Like you, we were also concerned about its low specificity." It turned out, he said, that the only statistically significant predictor of benefit was pathologic size, which isn't clinically useful. "We hope," he said, "that breast MRI specificity will improve as equipment and software improve.

Finally, Jose M. Velasco, M.D., of Rush University in Skokie, Il., asked whether MRI was used to evaluate lymph nodes, to which Dr. Bethke answered that there is no literature to support its use for this purpose. Sentinel node biopsy was used for this purpose.

To Dr. Valasco's question about whether there might be a role for MRI in directing breast cancer chemotherapy, Dr. Bethke answered that at this time the poor specificity and high cost rule this use out.