Preop MR cuts incidence of later breast cancer

Preoperative MR imaging of the opposite breast in women diagnosed with unilateral breast cancer increased cancer detection and was linked with reduced incidence of cancer in the opposite breast within 45 months, according to a study published online Jan. 17 in Radiology.

Women with unilateral breast cancer face an increased risk of breast cancer in the opposite breast; the incidence of synchronous cancer ranges from 1 to 5 percent and metachronous incidence is 3 to 13 percent. Although MR can depict contralateral cancers missed by other methods, the clinical effects of preoperative MR have not been established.

Jin You Kim, MD, from the department of radiology at Seoul National University College of Medicine in South Korea, and colleagues conducted a retrospective review to compare the incidence of synchronous and metachronous breast cancer of the contralateral breast in women with unilateral disease who underwent a preoperative MRI with those who underwent conventional imaging.   

A database search identified 1,771 women who underwent contralateral preoperative MRI, mammography and ultrasound (MR group) between January 2007 and December 2008, and 1,323 who underwent mammography and ultrasound (comparison group) between January 2004 and December 2006.

Preoperative mammography and ultrasound detected contralateral breast cancer in 1.2 percent of the women in the MR group and 1.4 percent of the women in the comparison group.

A total of 25 additional contralateral breast cancers were detected in the MR group compared with the conventional imaging group. Twelve of these cancers were ductal carcinoma in situ, and 13 were invasive.

The researchers noted one drawback of MR is its low specificity. However, the positive predictive value for MR-prompted biopsy was 51 percent in this study, which falls into the accepted range for clinical practice, according to Kim and colleagues.

In the 45 months following surgery, the cumulative incidence of contralateral breast cancer was 0.5 percent for the MR group and 1.4 percent for the comparison group.

Thus, the incidence of synchronous contralateral cancer was higher and incidence of metachronous contralateral cancer was lower in women who underwent a preoperative contralateral breast exam compared with those who did not.

“In addition, a particularly notable result of the multivariate Cox analysis was that contralateral MR imaging screening was an independent factor associated with a decreased incidence of metachronous cancer, in addition to ER positivity,” wrote Kim et al.

The researchers concluded by recommending that MR imaging of the breast is considered for preoperative evaluation of women with unilateral breast cancer.