MRI Detects Early Breast Cancer Cells

MRI screening has been considered less sensitive than
mammography for detecting precancerous cells in the breast which are confined
to the milk ducts, but a new study suggests the opposite is true.

Breast MRI detected 92% of surgically confirmed cases of ductal carcinoma in
situ (DCIS) in the German study, compared to a 56% detection rate for
mammography. Because DCIS often develops into invasive breast cancer, it is
almost always treated with surgery to remove all of the DCIS tissue.

The study appears in the Aug. 11 issue of the journal TheLancet.

In the U.S., magnetic resonance imaging (MRI) is currently recommended in
addition to an annual mammogram only for very high-risk women. But researcher
Christiane K. Kuhl, MD, of the University of Bonn, says the new findings could
mean a much broader use for breast MRI screening in the future.

"I would go so far as saying this is the beginning of the death of
mammography, but it is going to be a very, very slow death," Kuhl tells
WebMD.

"It will take many years before we have enough randomized prospective
trials to fully confirm our findings and enough radiologists who are qualified
to perform MRI to screen for breast cancer."

The Problems With MRI

Debbie Saslow, PhD, of the American Cancer Society, is unconvinced. She
tells WebMD that mammography is, and will remain, the screening tool of choice
for breast cancer for at least the next decade.

"We will see more technologies like MRI approved for use along with
mammography," she says. "But I don't know anyone who believes that any
of these technologies are candidates for replacing mammography."

Availability and cost are presently two important obstacles to a broader use
of breast MRI in the U.S., but they are not the only ones, Saslow says.

A breast MRI can cost $1,000 to $1,500 -- ten times the typical cost of
mammography. And there are currently not enough radiologists trained in the
procedure or dedicated breast MRI machines to provide screening to a larger
population of women.

But false positive results remain the biggest impediment to the use of
breast MRI in the screening of average-risk women, Saslow says.

The imaging technique is so sensitive that it finds many suspicious growths
that turn out not to be breast cancer (false positive), resulting in many
unnecessary biopsies.

In the roughly 2% of American women who are considered to be at high risk
for breast cancer, the benefits of screening MRI outweigh these risks, but
Saslow says this is not true for most other women.

"For average-risk women, the harms of MRI outweigh the risks," she
says. "In addition, there have been no studies, including the current one,
which assessed MRI screening of women who were not at high risk."

Roughly one in six (29 of 167) of detected DCIS cases in the study by Kuhl
and colleagues occurred among average-risk women. The rest, Saslow points out,
occurred in women with a known elevated breast cancer risk.

Ninety-three were referred for MRI because of abnormal mammograms, 18 had
been treated for breast cancer, and eight had family history of the
disease.

"The women in the study were not representative of the population at
large, so it doesn't tell us much about the use of MRI in average-risk
women," she says.

The Promise of MRI

About 20% of breast cancers now detected are confined to the milk ducts,
compared to just 2% prior to the widespread use of mammography.

In an editorial accompanying the German study, radiology professor Carla
Boetes, MD, PhD, of Radboud University in The Netherlands, writes that while
mammography had dramatically improved the detection of these very early breast
cancers, wider use of screening MRI might have an even greater impact.

"That only 20% of tumors detected through screening are pure DCIS is
disappointing, when one keeps in minthat most breast tumors probably evolve
from DCIS," she writes. "The observation that MRI detects many DCIS
lesions that go unnoticed on mammography implies that some invasive carcinomas
can be prevented by timely intervention on the basis of MRI findings."

By Salynn Boyles
Reviewed by Brunilda Nazario
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