‘Controversial’ preoperative breast MRI more accurate than mammography/ultrasound for many patients

A third of breast-cancer patients undergoing preoperative mammography and ultrasound would be more accurately imaged for tumor size with breast MRI, according to a study published online April 13 in the Journal of Surgical Oncology.

Researchers from the University of Chicago and NorthShore University Health System in Evanston, Ill., arrived at this conclusion by comparing concordance of pathology assessment of tumor size and foci with radiological assessment by MRI and combined mammography and ultrasound in 471 patients.

They deemed tumor size on imaging nonconcordant if it differed from the pathologic size by 33 percent or more. Tumor foci was deemed nonconcordant if more than one foci were seen in the lab.

If one or both of the mammography or ultrasound was nonconcordant and the MRI was concordant, they considered MRI as having provided the greater accuracy.

The team found that MRI was more accurate than mammography and ultrasound for 32.9 percent of the 471 patients for tumor size and for 21.9 percent for tumor foci.

Further, comparing patients for whom MRI had greater accuracy to those who did not, they found the only significant factor was calcifications on mammography. These were associated with MRI clinical accuracy for patients with invasive cancer.

Tumor size, stage, molecular subtype, histology, grade, patient BMI, age, mammographic density and use of hormone replacement therapy were not significantly different, the authors report.

“Breast MRI provides greater accuracy for a third of patients undergoing preoperative mammography and ultrasound,” lead author Jennifer Tseng, MD, of the University of Chicago and colleagues conclude.

In introducing their findings, Tseng et al. acknowledge that the use of breast MRI prior to surgery remains controversial.

“MRI has not been shown to improve local recurrence rates, re-excision rates or survival outcomes,” they write. “Preoperative MRI delays time from diagnosis to surgery. Furthermore, MRI findings have upgraded surgery from breast conservation to mastectomy.”

The authors cite a recent survey conducted by the American Society of Breast Surgeons showing that 41 percent of surgeons routinely use MRI in the preoperative setting.

“Interestingly, the most common reasons physicians reported to use MRI was not to improve the local recurrence risk or decrease re-excisions,” they write, “but to determine whether or not a patient was a candidate for breast conservation.”