LAS VEGAS – In women with higher density (HD) breasts, preoperative MRI revealed more abnormalities than were seen in women with lower density (LD) breasts, but there was no difference in the number of secondary cancers detected or long-term recurrence rates.
Breast density is often cited by radiologists as a reason to conduct a preoperative MRI, but the study suggests that it should not be a driving factor. “It’s a real challenge when our radiologists provide us reports that say, ‘Due to increased density, we recommend MRI,’ because it’s really hard to then disregard that. I think this is very important data,” said, professor of surgery at the Mayo Clinic, Rochester, MN, who moderated the session at the annual meeting of the American Society of Breast Surgeons where the research was presented.
“MRI is a valuable tool, and we’re still trying to figure out who it should be performed in,” said lead author, of the Mayo Clinic, Jacksonville, FL, in an interview.
The researchers retrospectively analyzed data from 683 women at their institution who underwent preoperative MRI between 2007 and 2011. They grouped them by mammography results into LD (33%; Breast Imaging–Reporting and Data System density, 1 and 2) and HD (67%; BI-RADS density, 3 and 4).
Patients in the HD group more often had ipsilateral MRI findings (42% vs. 31%; P = .005), but ,of those with MRI findings, a similar number of patients in each group needed a second site biopsy (HD 65% vs. LD 67%; P = .78).
In all patients who had an additional MRI finding, the odds of detecting an additional ipsilateral cancer were not statistically significant between HD (32%) and LD (23%; P = .15) patients.
HD patients were also more likely to have abnormalities in the contralateral breast (25% vs. 14%; P = .009), but there were no statistically significant differences in rates of second-site biopsy recommendations or in the percentages of abnormalities that turned out to be cancerous (HD 6% vs. LD 3%; P = 1.0).
Following MRI, 70% of LD patients expressed a preference for breast-conserving surgery, compared with 53% of HD patients (P = .0001).
Over a median 7 years of follow-up, there was no difference in freedom from recurrence rates between the two groups (91% in LD vs. 90% in HD; P = .57).
“To me, it says that you don’t have to order an MRI just because they have cancer in a high density breast. You can feel reassured by your surgical plan and treatment recommendations based on conventional imaging,” said Dr. McLaughlin.
The researchers can’t determine if having an MRI done increased patient worry and potentially led to the higher rate of mastectomies chosen by women in the HD group. “Is that a result of the MRI? I don’t think we can say that, but there’s this whole other discussion piece that goes into it. You definitely see patients who say, ‘But it found these other things, and I’m going to have a mastectomy.’ So, there’s that patient preference and worry piece,” said Dr. McLaughlin.
The study results should offer some reassurance to patients. “There were no differences in local recurrence rates according to density. Maybe the next angle is allaying some of that fear, because the outcomes were the same. It’s really driven more by tumor biology and multimodality therapy,” said Dr. McLaughlin.
The study doesn’t provide the final word on breast density and MRI, according to Dr. Boughey. “I think this is an area that needs to be studied more with a clinical trial. There are several going on in different countries, and this is an area where we need level 1 data. This study does fit with what many other studies have shown, which is that MRI probably doesn’t have as much benefit as patients believe it does, so our role really is to try to help educate patients.”