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Study finds pre-op MRI ups mastectomy rate

Knowing too much? Using magnetic resonance imaging to 'stage' a woman's breast cancer before surgery might do more harm than good, according to an Australian and US study.

MRIs produce a much clearer image than x-rays and ultrasound, and are recommended for detecting early tumours in women at increase risk for breast cancer. But routinely using the technology once any woman is diagnosed may lead to more radical surgery without any benefits, the researchers report in the Annals of Surgery .

They found that about 26 per cent of women who had a pre-operative MRI to help determine the extent and severity of their tumour ended up having their entire breast removed, compared to about 18 percent of those whose surgeons only used traditional methods of characterising the cancer.

"I wasn't surprised by the results at all. What I am surprised by is the strength of the data," says Monica Morrow, study co-author and the chief of breast service at Memorial Sloan-Kettering Cancer Center in New York.

Because MRIs are more sensitive than mammograms, some doctors think they are a good tool for identifying the precise outlines of cancerous tissue. Others, however, have begun to question whether the imaging led surgeons to remove more breast tissue than necessary.

Moreover, women who have MRIs before breast surgery seem to be no less likely to need a second surgery to remove additional cancerous tissue.

A study published in September, for instance, found that among more than 300 women who underwent breast cancer surgery, just as many of those who had an MRI before the first surgery ended up having a repeat operation.

For the study, Morrow, along with Associate Professor Nehmat Houssami and Dr Robin Turner of the University of Sydney, pulled together data from nine previous studies to see if MRIs influence the number of women who had their breast removed or who had a second surgery to remove additional cancer. From the nine studies, they had information on 3112 women who had breast cancer surgery.

Overall, the team found that about 16 per cent of the women who had an MRI ended up having the entire cancerous breast removed during their first surgery. That's compared to about 8 percent of women who did not have an MRI.

They also found that having an MRI before surgery did not influence whether women would need additional surgery to remove more tissue. In each group, between 11 percent and 12 percent had to have more surgery.

After taking into account the initial surgery and second operations, the researchers calculated that about 26 percent of those who had an MRI ended up having their entire breast removed, compared to 18 percent in the no-MRI group.

"It causes more mastectomies to start with, but it doesn't decrease the number of women who started out wanting a lumpectomy and needing a mastectomy," says Morrow of the pre-operative MRIs.

The study did not look at long-term outcomes, nor did it examine the use of MRI to screen the opposite breast for signs that cancer had spread, while the results do not apply to certain subgroups of patients, including women with genetic mutations that predispose them to cancer.

"There may be select circumstances where we'd use it to solve a problem, but for most women with breast cancer they don't need an MRI for their evaluation," says Morrow.