Although many risk factors may increase a woman’s chance of developing breast cancer, it is not yet known exactly how some of these risk factors cause cells to become cancerous. Hormones seem to play a role in many cases of breast cancer, but just how this happens is not fully understood.
Researchers are beginning to understand how certain changes in DNA can cause normal breast cells to become cancerous. DNA is the chemical in each of our cells that makes up our genes - the instructions for how our cells function. We usually resemble our parents because they are the source of our DNA. However, DNA affects more than how we look.
Some genes contain instructions for controlling when our cells grow, divide, and die. Certain genes that speed up cell division are called oncogenes. Others that slow down cell division, or cause cells to die at the right time, are called tumor suppressor genes. Cancers can be caused by DNA mutations (changes) that “turn on” oncogenes or “turn off” tumor suppressor genes.
INHERITED GENE MUTATIONS: Certain inherited DNA changes can cause an increased risk for developing cancer and are responsible for cancers that run in families. For example, the BRCA genes (BRCA1 and BRCA2) are tumor suppressor genes. Mutations in these genes can be inherited from one’s parents. When they are mutated, they no longer function to suppress abnormal growth, and cancer is more likely to develop.
Women have already begun to benefit several ways from recent advances in understanding the genetic basis of breast cancer. Genetic testing can identify some women who have inherited mutations in the BRCA 1 or BRCA 2 tumor suppressor genes. These women can take steps to reduce their risk of developing breast cancers and to monitor changes in their breasts carefully to find cancer at an earlier, more treatable stage.
Women with an inherited BRCA 1 or BRCA 2 mutation have up to an 80 percent chance of developing breast cancer during their lifetime, and when they do it is often at a younger age than woman who are not born with one of the mutations.
Normally, these genes help to prevent breast cancer by making proteins that keep cells from growing abnormally. However, if you have inherited a mutated copy of either gene from either parent, you are at and increased risk for breast and ovarian cancer.
ACQUIRED GENE MUTATIONS: Most DNA mutations related to breast cancer, however, occur in single breast cells during a woman’s life rather than having been inherited. These acquired mutations of oncogenes and/or tumor suppressor genes may result from other factors, such as radiation or cancer-causing chemicals. But so far, the cause of these mutations that could lead to breast cancer remains unknown. Most breast cancers have several gene mutations that are acquired.
GENETIC TESTING: There are tests that can tell if a woman has certain changed (mutated) genes linked to breast cancer. With this information, women can take steps to reduce this risk. Genetic counseling is strongly recommended before a woman has these tests and before she makes any decisions about preventive measures. Recently, the U.S. Preventive Services Task Force made recommendations for genetic testing. They recommended that only women with a strong family history be evaluated for genetic testing for BRCA mutations. This group is only about 2 percent of adult woman in the United States.
BREAST CANCER CHEMOPREVENTION: Chemoprevention is the use of drugs to reduce the risk of cancer. Several drugs have been studied for use in lowering breast cancer risk. The drug tamoxifen has already been used for many years as a treatment for some types of breast cancer. Now several studies have shown that women at high risk for breast cancer are less likely to get the disease if they take tamoxifen.
Another drug, raloxifene, has been approved to help reduce the breast cancer risk in women past menopause who are at high risk for breast cancer. Other drugs are also being studied.
PREVENTIVE PROPHYLATIC MASTECTOMY: For women who are at a very high risk for breast cancer, this surgery (a double mastectomy) may be an option. In this operation both breasts are removed before there is any known breast cancer. While this removes nearly all of the breast tissue, a small amount remains. So although the operation greatly reduces the risk of breast cancer, the disease can still develop in the breast tissue that remains after surgery. To date, this has been a rare problem.
The reasons for thinking about this type of surgery need to be very strong. There is no way to know ahead of time whether this surgery will benefit a particular woman. A second opinion is strongly recommended before making a decision to have this type of surgery.
PREVENTIVE PROPHYLATIC OOPHORECTOMY (preventive ovary removal): Women with a BRCA mutation who have their ovaries removed may reduce their risk of breast cancer by half or more. This is because taking out the ovaries removes the main sources of estrogen in the body.
Although this article is not about ovarian cancer, it is important that women with this gene change also know that they may have a high risk of getting ovarian cancer. Most doctors recommend that these women have their ovaries removed once child bearing is complete.
Additional information can be found at our website: www.cancer.org. The American Cancer Society provides cancer information and help 24 hours a day at 1-800-ACS-2345.
E-mail questions or comments to:joanieliebs@earthlink.net.
