While preoperative breast MRI rarely changes prior decisions to perform mastectomy on women with biopsy-proven breast cancer, the extra imaging can reduce the odds of needing a second trip under the knife for patients undergoing breast-conserving surgery.

That’s according to a study published online July 1 in the European Journal of Radiology.

Heike Preibsch, MD, of the University of Tübingen in Germany and colleagues reviewed the cases of 991 consecutive patients treated for one or more primary breast cancers in 2009 and 2010.

Sixty percent (599 patients with 626 cancers) were imaged with breast MR prior to surgery. The 40 percent who were not imaged preoperatively comprised the control.

The researchers found that the imaging changed the surgery in 25 percent of the MR+ cases (157 of 626).

Of these 157, some 81 percent (n = 127) benefited by the MRI: Previously occult cancers showed up in 122 patients and biopsy was avoided in another five.

Mastectomy rates did not differ between the MR+ and MR- group (39 percent vs. 39 percent).

However, on multiple regression analysis, the MR+ group had a lower chance for repeated surgery (p < 0.05).

The authors suggest preoperative breast MRI has the potential to reduce the rate of repeated surgeries without increasing mastectomy rates or delaying surgery.

Pre-op breast MRI “can possibly optimize treatment of patients with primary breast cancer,” Preibsch et al. write, “in particular if there is a higher risk of re-excision or conversion” from breast-conserving therapy to mastectomy.

“In our opinion, preoperative MRI should be performed in patients with biopsy-proven primary breast cancer if they are young and present with larger tumors and/or show equivocal findings on mammography and ultrasound,” they add.