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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