Causes of breast cancer
Studies continue to uncover lifestyle
factors and habits that alter breast cancer risk. Ongoing studies are
looking at the effect of exercise, weight gain or loss, and diet on
breast cancer risk.
Studies on the best use of genetic testing for BRCA1 and BRCA2
mutations continue at a rapid pace. Scientists are also exploring how
common gene variations may affect breast cancer risk. Each gene variant
has only a modest effect in risk (10 to 20%), but when taken together
they may potentially have a large impact.
Potential causes of breast cancer in the
environment have also received more attention in recent years. While
much of the science on this topic is still in its earliest stages, this
is an area of active research.
A large, long-term study funded by the
National Institute of Environmental Health Sciences (NIEHS) is now being
done to help find the causes of breast cancer. Known as the Sister
Study, it has enrolled 50,000 women who have sisters with breast cancer.
This study will follow these women for at least 10 years and collect
information about genes, lifestyle, and environmental factors that may
cause breast cancer. An offshoot of the Sister Study, the Two Sister
Study, is designed to look at possible causes of early onset breast
cancer. To find out more about these studies,
Chemoprevention
Fenretinide, a retinoid, is also being
studied as a way to reduce the risk of breast cancer (retinoids are
drugs related to vitamin A). In a small study, this drug reduced breast
cancer risk as much as tamoxifen.
Other drugs, such as aromatase inhibitors, are also being studied to reduce the risk of breast cancer.
For more information, see our document, Medicines to Reduce Breast Cancer Risk.
Making decisions about DCIS
In some women, DCIS turns into invasive
breast cancer and sometimes an area of DCIS contains invasive cancer. In
some women, though, the cells may never invade and remain localized
within the ducts. If the cells don’t invade, DCIS cannot be
life-threatening. The uncertainty about how DCIS will behave makes it
difficult for women to make decisions about what treatment to have, if
any. Researchers are looking for ways to help with these challenges.
Researchers are studying the use of
computers and statistical methods to estimate the odds that a woman’s
DCIS will become invasive. Some of these methods are based on routinely
available clinical information about the patient and her DCIS, whereas
others also include information about changes in her tumor’s genes.
Decision aids are another approach. They ask a woman with DCIS questions
that help her decide which factors (such as survival, preventing
recurrence, and side effects) she considers most important in choosing a
treatment.
Another recent area of research and debate
among breast cancer specialists is whether changing the name of DCIS to
one that emphasizes this is not an invasive cancer can help some women
avoid overly aggressive treatment.
New laboratory tests
Circulating tumor cells
Researchers have found that in many women
with breast cancer, cells may break away from the tumor and enter the
blood. These circulating tumor cells can be detected with sensitive lab
tests. Although these tests can help predict which patients may go on to
have their cancer come back, it isn’t clear that the use of these tests
will help patients live longer. They potentially may be useful in
patients with advanced breast cancer to help tell if treatments are
working.
Newer imaging tests
Several newer imaging methods are now being studied for evaluating abnormalities that may be breast cancers.
Scintimammography (molecular breast imaging)
In scintimammography, a slightly radioactive tracer called technetium sestamibi is injected into a vein. The tracer attaches to breast cancer cells and is detected by a special camera.
This technique is still being studied to see
if it will be useful in finding breast cancers. Some radiologists
believe it may helpful in looking at suspicious areas found by regular
mammograms, but its exact role remains unclear. Current research is
aimed at improving the technology and evaluating its use in specific
situations such as in the dense breasts of younger women. Some early
studies have suggested that it may be almost as accurate as more
expensive magnetic resonance imaging (MRI) scans. This test, however,
will not replace your usual screening mammogram.
Tomosynthesis (3-D mammography)
This technology is basically an extension of
a digital mammogram. For this test, the breast is compressed once and a
machine takes many low-dose x-rays as it moves over the breast. The
images taken can be combined into a 3-dimensional picture. This uses
more radiation than most standard 2-view mammograms, but may have the
advantage of seeing problem areas more clearly, possibly finding more
cancers. Still, more studies comparing breast tomosynthesis to standard 2
view mammograms are needed to know what role this technology will have
in screening and diagnosis of breast cancer.
Several other imaging methods, including thermal imaging (thermography) are discussed in our document, Mammograms and Other Breast Imaging Procedures.
Treatment
Oncoplastic surgery
Breast-conserving surgery (lumpectomy or
partial mastectomy) can often be used for early-stage breast cancers.
But in some women, it can result in breasts of different sizes and/or
shapes. For larger tumors, it might not even be possible, and a
mastectomy might be needed instead. Some doctors address this problem by
combining cancer surgery and plastic surgery techniques, known as oncoplastic surgery.
This typically involves reshaping the breast at the time of the initial
surgery, and may mean operating on the other breast as well to make
them more symmetrical. This approach is still fairly new, and not all
doctors are comfortable with it.
New chemotherapy drugs
Advanced breast cancers are often hard to treat, so researchers are always looking for newer drugs.
A drug class has been developed that targets cancers caused by BRCA mutations. This class of drugs is called PARP inhibitors and
they have shown promise in clinical trials treating breast, ovarian,
and prostate cancers that had spread and were resistant to other
treatments. Further studies are being done to see if this drug can help
patients without BRCA mutations.
Targeted therapies
Targeted therapies are a group of newer drugs that specifically take advantage of gene changes in cells that cause cancer.
Drugs that target HER2: A number of
drugs that target HER2 are currently in use, including trastuzumab
(Herceptin), pertuzumab (Perjeta), ado-trastuzumab emtansine (Kadcyla),
and lapatinib (Tykerb). Other drugs are being developed and tested.
Anti-angiogenesis drugs: For cancers to grow, blood vessels must develop to nourish the cancer cells. This process is called angiogenesis.
Looking at angiogenesis in breast cancer specimens can help predict
prognosis. Some studies have found that breast cancers surrounded by
many new, small blood vessels are likely to be more aggressive. More
research is needed to confirm this.
Bevacizumab (Avastin) is an example of
anti-angiogenesis drug. Although bevacizumab turned out to not be very
helpful in the treatment of advanced breast cancer, this approach still
may prove useful in breast cancer treatment. Several other
anti-angiogenesis drugs are being tested in clinical trials.
Other targeted drugs: Everolimus
(Afinitor) is a targeted therapy drug that seems to help hormone therapy
drugs work better. It is approved to be given with exemestane
(Aromasin) to treat advanced hormone receptor-positive breast cancer in
post-menopausal women. It has also been studied with other hormone
therapy drugs and for treatment of earlier stage breast cancer. In one
study, letrozole plus everolimus worked better than letrozole alone in
shrinking breast tumors before surgery. It also seemed to help in
treating advanced hormone receptor-positive breast cancer when added to
tamoxifen. Everolimus is also being studied in combination with
chemotherapy and the targeted drug trastuzumab. Other drugs like
everolimus are also being studied.
Other potential targets for new breast
cancer drugs have been identified in recent years. Drugs based on these
targets are now being studied, but most are still in the early stages of
clinical trials.
Bisphosphonates
Bisphosphonates are drugs that are used to
help strengthen and reduce the risk of fractures in bones that have been
weakened by metastatic breast cancer. Examples include pamidronate
(Aredia) and zoledronic acid (Zometa).
Some studies have suggested that zoledronic
acid may help other systemic therapies, like hormone treatment and chemo
work better. In one study of women being treated with chemo before
surgery, tumors in the women getting zoledronic acid with chemo shrank
more than those in the women treated with chemo alone.
Other studies have looked at the effect of
giving zoledronic acid with other adjuvant treatment (like chemo or
hormone therapy). So far, the results have been mixed. Some studies have
shown that this approach helped lower the risk of the cancer coming
back, but others did not. The results of one study linked the use of
these drugs with adjuvant chemo with an increased risk of breast cancer
recurrence in younger women. Overall, the data does not support making
bisphosphonates part of standard therapy for early-stage breast cancer.
Denosumab
Denosumab (Xgeva, Prolia) can also be used
to help strengthen and reduce the risk of fractures in bones that have
been weakened by metastatic breast cancer. It is being studied to see if
it can help adjuvant treatments work better.
Vitamin D
A recent study found that women with
early-stage breast cancer who were vitamin D deficient were more likely
to have their cancer recur in a distant part of the body and had a
poorer outlook. More research is needed to confirm this finding, and it
is not yet clear if taking vitamin D supplements would be helpful.
Still, you might want to talk to your doctor about testing your vitamin D
level to see if it is in the healthy range.
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