Most women in the United States who have
a mammogram this year will receive good news; there is
nothing wrong. For the relatively small number of women
with abnormal mammogram results, or for those who seek
medical attention because of a new breast symptom, advances
in the diagnosis of breast disease now permit more rapid
and more accurate evaluation of such problems.
Breast cancer is not one type of disease
with one treatment option, namely metastatic invasive
ductal breast cancer and mastectomy is your only option.
Breast cancer comprises a whole spectrum of diseases from
the low grade form called ductal carcinoma in situ (DCIS)
to invasive non-metastatic cancer to metastatic cancer.
The reason this is important is because the tools I am
about to describe to you with the exception of the first,
namely mammography, can’t diagnose the low grade DCIS
form well at all and DCIS accounts for up to 30% of breast
cancers detected today and also because these are the
cancers we want to find most. This is because the smaller
the cancer and the lower the grade cancer at the time
of diagnosis, the better the chance for cure and the longer
the survival. “Are you surprised that the best technique
for screening women yearly beginning at age 40 still remains
mammography?” Don’t be. Breast cancer comes basically
in three forms: Masses, calcifications, and masses that
contain calcifications.
Calcifications by themselves in the breast,
if malignant, usually represent the low end of the spectrum,
DCIS, and the only imaging tool that works is mammography.
But we are improving detection capability. Film screen
mammography involves minimal radiation exposure. A skilled
technologist takes two x-ray pictures of each breast from
two directions. At least one radiologist, a doctor specializing
in imaging the breast, reads the mammogram.
Having 2 radiologists read your mammogram
reduces the chance of missing a problem by about 10-15%.
Some centers routinely have your mammogram read twice,
but this is expensive and most insurance companies won’t
pay for it. You can also get a second opinion on your
mammogram from a computer. This is called Computer Aided
Detection or CAD. The computer finds any areas that have
any extra thickness to it. The doctor then examines each
area and decides if it needs further evaluations. On a
mammogram, the gland tissue in the breast looks dense;
this means that it is thick or hard to see through. Some
women have denser breasts than others. Dense breasts have
more glandular and connective tissue and less fat tissue.
Younger women tend to have denser breasts than older women.
And thinner women tend to have denser breasts than heavier
women. Breast cancer is also made up of dense tissue.
This means that on a mammogram, a breast cancer can be
harder to spot in dense breasts. This is because the cancer
can look a lot like the gland tissue around it.
In CAD, the computer can see though this
tissue eliminating the need for extra x-ray pictures taken.
Because CAD is a relatively new technology, researchers
are still looking at how much it can help radiologists
to detect breast cancer on mammograms.
One potential problem with CAD is that
it gave significantly more false positive readings in
dense breasts compared with non-dense breasts. This means
that CAD is more likely to suggest an abnormality that
isn’t really there in a dense breast than in a nondense
breast. It is important to find breast cancer early, when
it’s more readily treated. Because no test so far has
proven to be flawless for early detection, it is also
important to combine current methods to increase the chance
of early detection. Radiologists are likely to miss seeing
a cancer on a mammogram when they use a CAD or second
reader to back them up.
The sensitivity of mammography is pretty
good, about 90%; but the specificity is low, only in the
40-50% range. In other words, mammography will find an
abnormality, but is not very good at saying what the abnormality
represents. Magnetic Resonance Imaging (MRI), a relatively
new technique could add important information to an initial
diagnosis and can add important components to care once
a diagnosis of breast cancer is made.
Magnetic resonance breast imaging, also
known as MRI, has been approved by the FDA since 1991
for use as a supplemental tool, in addition to mammography,
to help diagnose breast cancer; but it is only recently
that the technology has caught up with the research so
that MRI is only now just coming into its own. Breast
MRI is an excellent problem solving technology. It is
often used to investigate breast concerns first detected
with mammography, physical exam or other imaging exams.
MRI is also excellent at imaging the augmented breast;
including both the breast implant itself and the breast
tissue surrounding the implant. Abnormalities or signs
of breast cancer can sometimes be obscured by the implant
on a mammogram. MRI is also useful for staging breast
cancer, determining the more appropriate treatment, for
patient follow up after breast cancer treatment. I use
it in the following scenarios:
Patient newly diagnosed with breast cancer and has
dense breasts to look for additional hidden sites of
cancer in either breast.
For large cancers that need to be shrunken down prior
to surgery by using chemotherapy. MRI shows accurately
its pre-treatment and post-treatment size.
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For distinguishing scar from recurrent
cancer in problem cases.
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For following cancer survivors
with dense tissue.
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For implant problems and other
problem solving needs in difficult cases.
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For research currently ongoing
at Memorial as to the value in
screening young women at high risk for the disease.
Most women under age 40 years of age do not require any
breast imaging. However, some of these younger women are
at high risk of breast cancer as determined by a strong
family history or a mutated breast cancer gene called BRCA
1 or 2 and therefore need breast imaging before 40. MRI
may be helpful for these women because technology is effective
in dense breast tissue and most young women have dense breasts.
However, mammography is currently the only FDA approved
exam to be used to screen for breast cancer in women with
no symptoms of the disease. Even if MRI one day gains approval
as a breast cancer screening tool for women at high risk
of the disease, it would most likely be used in conjunction
with mammography of select women. Like Positron Emission
Tomography, PET scanning, which I will discuss next, MRI
is limited in its ability to see low grade DCIS, the kind
that presents most often as microcalcifications. In the
case of MRI, this is because the agent used to highlight
the cancer takes advantage of that fact that cancer creates
its own and enhanced blood supply to help it gr w, with
the exception of DCIS, which can live happily off the normal
blood supply in the breast for some time before something
triggers it to become more aggressive. Without an increased
blood supply, the area on MRI will not likely become highlighted.
P E T scan imaging as you will soon see has a similar problem
picking up low grade cancer because PET scanning takes advantage
of a cancer cell’s voracious appetite with the exception
of low grade DCIS, which is perfectly happy utilizing the
available food supply.
So how is MRI performed? Unlike mammography which uses
low dose x-rays to image the breast MRI uses powerful magnetic
fields and radio waves to create images of the breast. The
main component of most MRI systems is a large tube shaped
magnet. To begin the exam, the patient is positioned on
a special table inside the MRI system opening where a magnetic
field is created by the magnet. During the exam a radio
signal is turned on and off, and subsequently, the energy
which is absorbed by different atoms in the body is echoed
back out of the body. These echoes are measured by the MRI
scanner. A digital computer reconstructs these echoes into
images of the breast. The loud tapping sound heard during
the MRI exam is created when coils are switched on and off
to measure the echoes. A benefit of MRI is that is can easily
acquire direct views of the breast in almost any orientation
while mammography requires reorientation of the breast.
MRI does not use any radiation. An MRI exam typically takes
between 30 and 60 minutes. The most useful MRI technique
for breast imaging uses a contrast material called gadolinium,
which is injected into a vein in the arm before or during
the exam to improve the quality of the images. This contrast
agent helps produce stronger and clearer images and highlight
any abnormalities.
MRI is highly sensitive to small abnormalities that can
sometimes be missed on routine mammography. Dense breast
tissue does not hinder MRI like it does in mammography.
As stated earlier, I use it now fairly frequently to assess
for additional sites of tumor once a diagnosis is made.
This is very important because one tumor site can often
be treated by removing the lump by lumpectomy, whereas multiple
tumors will likely require mastectomy. It doesn’t help a
woman to treat one site only if more exist in the breast.
She will only do battle with it in the future. I used to
perform a full sonograph on both breasts to achieve the
same goal as MRI and while no single study to date has put
MRI head to head with sonograms, in my experience, MRI probably
picks up slightly more tumors and sizes them more accurately
than sonograms. Furthermore, sonography is very user dependent,
and while I am very comfortable using it, many doctors aren’t.
MRI studies are fairly uniform from doctor to doctor and
institution to institution.
MRI still has additional hurdles to undergo in order to
gain wider acceptance and use. First, MRI cannot always
distinguish between cancerous and non-cancerous abnormalities,
which can lead to unnecessary breast biopsies. Its specificity
is not terrific. A b i o psy of an MRI detected abnormality
can be particularly d i fficult. It is because there is
little experience out there on how to biopsy under MRI and
some things we see only on MRI and it can therefore only
be sampled in this manner. Happily, Memorial Sloan Kettering
has a magnet friendly biopsy machine. MRI is also an expensive
exam. An average MRI of the breasts costs approximately
$1000 versus $150 for a mammogram. MRI can also take longer
than mamm o g r a p h y, more than 30 minutes in addition
to the administration of the contrast material. Patients
need to lie still face down during the exam to eliminate
motion in the images. Though an MRI exam is not in the least
bit painful, patients must tolerate any claustrophobia.
Finally, MRI is not widely available for breast imaging.
Currently, breast MRI is performed mostly at research centers.
MRI of the breast is currently covered by Medicare for all
the reasons I currently use it with the exception of ongoing
research in its effectiveness as a screening tool in high
risk young women.
Positron Emission Tomography (PET) was available about
20 years ago. The procedure became clinically feasible only
with the more recent changes in technology that produced
high quality images. The way in which it works is totally
novel. CT scanning and mammography show anatomy and do so
with administering varying doses of x-ray radiation. MRI
and Ultrasound also show anatomy, showing how abnormalities
are related to other structures and what they look like
in terms of shape and size. PET s c a n n i n g takes advantage
of the metabolism of cancer cells. When you have a PET scan,
you are injected with a very small amount of radioactive
material tagged to glucose, the main food source of all
cells. You lie in a short tube for about 5 minutes in each
of several positions and a full body holographic like image
from head to pelvis is created. Active cells take up the
radioactive material. Because cancer cells are usually more
active than normal cells, they are more likely to take up
the radioactive food material. A r e a s that take up the
material show up on the PET s c a n images. This helps radiologists
identify areas where a cancer might be growing. PET scans,
in other words, not only show where a cancer is growing,
but shows whether cancer cells are active. This means that
if something looks abnormal, PET can go one step further
and see whether the abnormality is active and growing or
inactive and shrinking. Very few things are as metabolically
active as cancer tumors. False positives (think its cancer
but really isn’t) aren’t much of a problem The glucose tag
is generally very good for defining recurrent tumor or metastases.
PET is at the cutting edge of diagnosis for many initial
tumors, too, but not for tiny ones such as many breast tumors
less than 1-2 centimeters in size. This is the size, by
the way, that we routinely pick up on high quality mammograms.
PET scanning will not replace the mammogram. PET scanning
for breast cancer is most important as a tool for checking
for cancer that has spread outside the breast to other body
parts. It is extremely helpful when planning radiation because
CT scan alone can only delineate the mass and frequently
fails to determine reliably the amount and extent of viable
tumor. P E T scanning for metastases is 93% sensitive and
84% specific. PET scanning has been found to be better than
other imaging tests at finding cancer recurrence in previously
treated women. If PET scans find evidence of recurrence,
women can begin appropriate treatment early to try to get
rid of the recurring cancer or at least delay its growth.
Wo m e n already treated for invasive breast cancer and
who are at high risk of recurrence are usually followed
carefully by their doctors to see if everything is okay.
Compared to the many different tests that can be used, PET
scans may offer some advantages. P E T is more likely than
other tests to find something t h a t ’s wrong, and it’s
more likely to give an accurate prediction about how active
the cancer is. If you’ve been treated for invasive breast
cancer and are at a high risk of recurrence, ask your doctors
about the possibility of getting a PET scan. But keep in
mind that PET scans are expensive and not available in all
locations. Getting the cost of PET scans covered by insurance
can be a challenge. Medicare now covers the cost of PET
scans for women with known metastatic disease. But for women
with high-risk disease in the breast and positive lymph
nodes, PET scan costs might not be covered. Remember too
that the conventional or non-PET tests performed are also
quite effective and still offer important value. Before
you get a test, it’s important to be sure that the test
is worth getting. Remember that if the PET scan predicts
recurrence, your doctor might recommend more aggressive
treatment. You should discuss all treatment options with
your doctor before and after the PET scan to decide which
treatment would be best for you. It is also important to
remember that detecting recurrence may mean that you get
aggressive treatment before it is high quality of life without
the side effect of aggressive treatment. It is very important
to weigh all the pros and cons of earlier detection before
you decide to go ahead with this test. I am encouraged by
the recent addition of these new technologies. I believe
that they have improved patient care and will prove to decrease
morbidity and mortality from breast cancer; and I promise
to continue to keep you informed of all the most promising
new technologies as we work with them. |
