Yesterday, while scouring KevinMD, I stumbled across a post from “Respectful Insolence,” a blog authored by an academic surgeon/scientist who dubs himself “Orac.” In the post, Orac reports that this Wednesday at the American Society of Clinical Oncology (ASCO) 2008 Annual Meeting,researchers from the Mayo Clinic will be reporting on a disturbing correlation between the use of breast magnetic resonance imaging (MRI) and a rise in the number of women having mastectomies. In this context, Orac offers a cogent, compelling perspective on why too much cancer screening can harm patients.
Orac’s worries specifically relate to using MRI scans to detect breast cancer. Advocates of the procedure rightly claim that MRI scans can detect more growths than other techniques, including mammography [i.e. an x-ray] and a clinical examination. The MRI technology detects so much that, as the New York Times put it last year, the scans reveal “all sorts of suspicious growths in the breast, leading to many repeat scans and biopsies for things that turn out to be benign.”
In other words, breast MRI scans are so sensitive that if you have breast cancer, there’s an almost 100 percent chance that they’ll detect it; but the technology produces many false positives because it’s not as good at distinguishing between malignant and benign growths. As Orac puts it: “…MRI [scans] now routinely "section" people into "slices" much thinner than 1 cm, making our imaging sensitivity considerably higher than it was 14 years ago.
The problem is that while many people undergo malignant changes in various organs as they grow older than most will never actually develop “clinically apparent cancer.” In fact, some studies have shown that MRI scans accurately detect breast cancer just 30 percent of the time. Though most studies place this rate at a higher level, they also show that mammographies (using x-rays to examine the breast) lead to fewer false positives than MRI scans.
The problem with high sensitivity but many false positives (what clinicians call “low specificity”) is obvious. Orac
again: “[MRI] picks up all sorts of lesions that mammography misses,
but most of them are not cancer.” You might guess that this dynamic
would result in more patients freaking out about having breast cancer
and taking relatively drastic measures to deal with it—say, having full
mastectomies. You would be right.
This brings us to the Mayo Clinic report
that will be presented Wednesday at ASCO’s annual meeting. The
researchers at Mayo looked at correlations between MRI scans and
mastectomies among 5464 women who had surgery for early-stage breast
cancer at the Mayo Clinic between 1997 and 2006. They found that rates
of mastectomies fell from 45% in 1997 to 30% in 2003, but then rose to
43% in 2006. This recent uptick was coupled with an increase in the use
of breast MRI scans in the clinic: the number of women who underwent
these scans doubled from 11% in 2003 to 22% in 2006. In that year, more
than half the women (52%) who underwent an MRI scan at Mayo went on to
have a mastectomy. In contrast, only 38% of women who did not have an
MRI had a mastectomy in 2006.
According to Dr. Rajini Katipamula, lead researcher of the study, these
data “demonstrate that a significant number of women with early-stage
breast cancer are undergoing mastectomy, and it appears to be partially
related to the introduction of preoperative MRI.” The scans detect more
tissue growth, which makes patients more worried that they have
cancer—and one would guess, sparks concerns that the cancer is
widespread, depending on how many growths are detected. So women are
increasingly undergoing mastectomies—total removal of the
breast—instead of getting a mammography, a lumpectomy (tumor removal)
or radiation therapy (zapping cancer cells with high-energy particles).
Orac points out that a big problem here: survival rates for patients
undergoing mastectomies are the same as for those undergoing other,
less severe procedures such as lumpectomies or radiation therapy. And
there is also no evidence that using an MRI scan to detect cancer
reduces mortality rates. This is an important consideration. Indeed, we
should always ask ourselves the following question posed by Orac: “Does
finding more disease before surgery that wouldn’t have been found
before [surgery] improve outcomes and survival rates?”
So are we 100 percent sure that more MRI scans is causing more
mastectomies? No—correlation is not causation, so theirs is no
definitive cause-and-effect relationship between more MRI and more
mastectomies. But it sure seems likely, particularly when compared to
For example, Matthew Goetz, a co-author of this week’s Mayo study, suggests
that an increase in mastectomies might have to do with advances in
reconstructive surgery that make the prospect of losing both breasts
less frightening than it once was. But this isn’t a terribly compelling
explanation. Breast reconstruction is no walk in the park. Mastectomy
patients can get breast implants which will probably need to be
replaced over the years and can cause pain or infections. Another
option is tissue flap procedures, which take tissue from one part of
the body (usually the stomach or upper back) to reconstruct the breast.
According to the American Cancer Society,
this isn’t a picnic either: “There can…be complications at the donor
sites, such as abdominal hernias and muscle damage or weakness. There
can also be differences in the size and shape of the 2 breasts. Because
blood vessels are involved, these procedures usually cannot be offered
to women with diabetes, connective tissue or vascular disease, or to
The big problem with all this, of course, isn’t just that women are
undergoing more mastectomies—but that, because MRI scans have a
relatively high rate of false positives, that women are undergoing more
unnecessary mastectomies. This is especially worrisome given
that the sensitivity of MRI scans are so high that, once cancer has
been found in one breast, they are increasingly being used to detect
early-stage cancer in the other breast. This means we may well be
seeing an increase in double mastectomies over time. Indeed we already have seen a rise–although MRI scans are not the only reason for this trend.
As Dr. Seema Khan, director of the program for early detection and
prevention of breast cancer at Northwestern Memorial Hospital, is
quoted as saying on Orac’s blog, "there’s a huge question of whether
we’re being led down a path of overtreatment by routinely using MRI.”
As is so often the case in American medicine, the emergence of a new
technology has briskly outpaced our knowledge of how to best utilize
it—and of its associated risks.
Indeed, Orac notes that the results of “mammography and ultrasound,
along with clinical assessment,” have been “validated over three
decades with large clinical trials.” When it comes to MRI scans,
however, “there is no evidence yet…[that they]in any way leads to
improved survival in breast cancer.” What we do know is that the
all-seeing eye of the MRI “can…influence a clinician’s and woman’s
decision” about how to respond to breast cancer—or to something that
might or might not be breast cancer.
The rush to MRI creates other problems. A breast MRI scan costs at least $1,000, and generally anywhere from 10-15
times as much as mammography. Because MRI machines are so expensive,
they also tend to be concentrated in high-income metropolitan
hospitals, raising issues of access. And though breast MRI can be
covered by Medicare, local Medicare contractors have wide discretion to determine the circumstances under which a MRI scan is covered.
But really, this isn’t about money or health coverage. It’s about the
fact that—as Orac succinctly puts it—“more is not always better.”