Research into the causes, prevention, and treatment of breast cancer is under way in many medical centers throughout the world. Our document, Breast Cancer (in women) contains more information on advances in treatment because almost all breast cancer clinical trials and research are done in women.

Causes of breast cancer and breast cancer prevention

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. Some studies have found that men with mutations in these genes may be more likely to develop some other cancers, including prostate cancer, stomach cancer, pancreas cancer, and melanoma. The risks for these cancers will be further defined in future studies.

Other genes that contribute to breast cancer risk are also being identified. This will occur more rapidly now that the human genome has been sequenced.

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.

New laboratory tests

Gene expression studies

One of the dilemmas with early stage breast cancer is that doctors cannot always accurately predict who has a higher risk that the cancer will come back after treatment. That is why almost everyone, except for those with small tumors, receives some sort of adjuvant treatment after surgery. To try to better pick out who will need adjuvant therapy, researchers have looked at many aspects of breast cancers.

In recent years, scientists have been able to link certain patterns of genes with more aggressive breast cancers in women -- those that tend to come back and spread to distant sites. Some lab tests based on these findings, such as the Oncotype DX and MammaPrint tests, are already available, although doctors are still trying to determine the best way to use them. It is not yet clear how useful these tests might be in men. For more information, see the separate American Cancer Society document, "Breast Cancer."

Tests of HER2 status

Determining a breast cancer's HER2 status is important, both to get an idea of how aggressive the cancer might be and to find out if certain drugs that target HER2 can be used to treat the disease.

Two types of tests -- immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) -- are currently used to determine HER2 status. The FISH test is generally thought to be more accurate, but it also requires special equipment, which can make testing more expensive.

A newer type of test, known as chromogenic in situ hybridization (CISH), works in a similar way to FISH -- by using small DNA probes to count the number of HER2 genes in breast cancer cells. But this test looks for color changes (not fluorescence) and doesn't require a special microscope, which may make it less expensive. And unlike other tests, it can be used on tissue samples that have been stored in the lab.

Some studies have suggested that another new test, which more precisely measures the amount of HER2 protein in cancer cells than current tests, may be better able to identify cancers that are likely to respond to HER2-targeted drugs such as trastuzumab (Herceptin).

Circulating Tumor Cells

Researchers have found that in many breast cancers, cells may break away from the tumor and enter the blood. These circulating tumor cells can be detected with sensitive lab tests. These tests are not yet available for general use, but they may eventually help find out if a treatment (such as chemotherapy) is working or to detect cancer recurrence after treatment.

Treatment

Radiation therapy

For men who need radiation after breast-conserving surgery, newer techniques may be as effective while offering a more convenient way to receive it (as opposed to the standard daily radiation treatments that take several weeks to complete).

Hypofractionated radiation: Doctors are comparing giving larger daily doses of radiation over fewer days to the standard radiation schedule. Studies have shown that in women, giving radiation over 3 weeks seems to be about as effective as the standard 5-week course. Other studies are looking at giving even larger daily doses over an even shorter time, such as a week.

Chemotherapy

Dose dense chemotherapy: Some recent research has suggested that giving chemotherapy more often (every 2 weeks) at the usual doses may work better in preventing recurrence than the usual schedule (every 3 weeks). Because of this aggressive schedule, drugs called growth factors must be given to prevent low blood counts, a common and serious side effect of chemotherapy. Some doctors already commonly use this approach, but clinical trials are in progress to better define the role of dose density in adjuvant therapy.

New chemotherapy drugs: Because advanced breast cancers are often hard to treat, researchers are looking for newer drugs. One example of a promising new drug is ixabepilone. This drug has been found to cause a significant percentage of breast tumors to shrink or stop growing, even in some people who have already had several types of chemotherapy.

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: Trastuzumab (Herceptin) is a monoclonal antibody (a manmade version of a specific immune system protein) used to treat breast cancer. It works by preventing the HER2 protein from promoting excessive growth of breast cancer cells and may also help the immune system fight the cancer.

Lapatinib (Tykerb) is a small molecule targeted therapy taken in pill form, and has recently been FDA approved for use in HER2-positive advanced breast cancers that are growing despite the use of trastuzumab.

Other drugs that target the HER2 protein are being tested in clinical trials.

Anti-angiogenesis drugs: In order 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 anti-angiogenesis drug that has shown promise when used in combination with the chemotherapy drug paclitaxel (Taxotere) in patients with metastatic breast cancer.

Other new drugs are also being developed that may be useful in preventing new blood vessels from forming. Several of these drugs are now being tested in clinical trials

Drugs that target EGFR: The epidermal growth factor receptor (EGFR) is another protein found in high amounts on the surfaces of some cancer cells. Some drugs that target EGFR, such as cetuximab (Erbitux) and erlotinib (Tarceva), are already used to treat other types of cancers, while other anti-EGFR drugs are still considered experimental. Studies are now under way to see if these drugs might be effective against some types of breast cancer.

Other targeted drugs: Many other potential targets for new breast cancer drugs have been identified in recent years. Drugs based on these targets are now being studied, although most are still in the early stages of clinical trials.

Last Medical Review: 09/24/2008
Last Revised: 05/13/2009