Breast MRI leads to necessary tumor detection, not unnecessary mastectomy

Dec 3, 2000

A commonly voiced fear regarding breast MRI is that it may offer too much information and lead to overtreatment. A study from the University of Pittsburgh, however, found that the modality did not result in an inordinate increase in the hospital's mastectomy rate. In addition, MRI found lesions that neither mammography nor ultrasound were able to detect.

Dr. Lara Hardesty from the university's Magee Women’s Hospital presented the results of the study at the RSNA conference on Thursday. The goal of the paper was to determine whether the use of breast MR to evaluate the extent of disease in patients with known breast cancer changed the rate of mastectomy.

From the hospital’s tumor registry, the group extracted 40 patients who had undergone mastectomy in 1999 for the treatment of breast cancer. The researchers evaluated the MR imaging-based recommendation for the type of surgery, either mastectomy or segmental mastectomy.

"All patients with needle biopsy-proven breast cancer who underwent preoperative breast MRI to evaluate the extent of their disease were included," Hardesty said. "During clinical interpretation of the breast MRI, the breast imager recorded the mammogram and/or ultrasound-based recommendation, whether that was for segmental mastectomy or mastectomy. Then the breast imager recorded whether the MRI changed that recommendation."

Forty patients underwent mammography, with or without ultrasound, before having a breast MR scan. In 60% (24 patients) of the cases, the mammography and ultrasound results led to a recommendation for segmental mastectomy, Hardesty said. After MRI, the treatment protocol was changed to mastectomy in seven of these 24 patients (30%).

"The change in recommendation was due to the detection of previously unsuspected multicentric cancer in four patients, and tumors larger than previously suspected on conventional imaging in three patients," Hardesty explained.

In 40% of the patients who had non-determinate findings on both mammography and ultrasound, MRI definitively showed that mastectomy would be the best treatment. In some of these cases, the MR findings contradicted patient wishes or the surgeon’s reluctance to go ahead with mastectomy.

Hardesty cited one example in which mammography detected two spiculated masses: one in the upper outer quadrant and one posterior to the inferior aspect of the breast.

"Percutaneous biopsy confirmed that both sites were breast carcinoma," she said. "The patient remained hesitant to undergo mastectomy, so MRI was performed. MRI actually showed that the carcinoma extended between the two mammographically detected foci. The MRI finding of the cancer being larger than suspected mammographically helped convince the patient of the need for mastectomy."

In another case, a patient presented with two palpable masses on the upper outer quadrant of the left breast. Both masses were seen on mammography and ultrasound exams. MRI showed extensive malignancy throughout the breast, including the lower inner quadrant, Hardesty said.

"Ultrasound after MRI could not identify these additional suspicious areas. At mastectomy, there was extensive invasive ductal carcinoma through the breast, including the lower inner quadrants and the two palpably known cancers. MRI detected multicentricity that was not detectable at mammography and ultrasound," she added.

Overall at Magee in 1999, the rate of segmental mastectomy was 75% and the rate of mastectomy was 25% among 500 patients. MR findings changed the imaging-based recommendation in seven of these 500, increasing the rate of mastectomy by 1.4%, Hardesty said.

Future studies will examine whether MRI-directed mastectomy will affect recurrence and survival rates, Hardesty concluded.

By Shalmali Pal
AuntMinnie.com staff writer
December 4, 2000

MRI best for evaluating breast tumors before surgery, January 26, 2000

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