Breast Cancer
Breast cancer usually arises from ducts in the breast. At first, it may be confined within the ducts, in which case it is known as ductal carcinoma in situ (DCIS). At this stage, it does not have the potential to spread outside the breast. However, at some point, the cancer can become invasive, meaning that it spreads outside the breast ducts and replaces normal breast tissue with a tumor mass. This progression describes the most common breast cancers.
The first theory about the way breast cancer spreads held that it starts in the breast and spreads in an orderly fashion to the surrounding region that includes the chest wall muscles and lymph nodes, eventually invading blood vessels and distant organs. This theory led to the first breast cancer treatment, radical mastectomy, a surgery in which chest muscle is removed along with the breast and all the lymph nodes under the arm. It was thought that radical surgery was necessary to cure the cancer because it removed the areas of potential invasion.
A more recent theory holds that, from the start, breast cancer is a systemic disease, meaning that cells have likely escaped the breast very early, often bypassing the lymph nodes. This is why systemic treatments, those that travel throughout the bloodstream, came into use. In reality, no ultimate theory for the progression of breast cancer exists, and the truth is likely a combination of these two theories. Some cancers may be cured with surgery alone, but most benefit from a combination of treatment strategies.
Risk Factors and Genetic Testing
Risk factors for developing breast cancer include age, hormonal factors, certain benign breast conditions, family history, and, of course, being female (ninety-nine out of one hundred breast cancers occur in women). Because breast cancer is a common disease, it is not uncommon to have a relative that has breast cancer. However, this does not imply that an abnormal gene is being passed down from generation to generation. In fact, less than 10 percent of all breast cancers are caused by a known inherited genetic defect, or mutation. The most common of these mutations occur in two genes, BRCA-1 or BRCA-2. Both genes normally play a role as a tumor suppressor and in DNA repair, so mutations in these genes allow damaged cells to grow out of control.
Mutations have been found less commonly in other genes, but doctors are sure they’ll find more. People who have an inherited mutation in BRCA-1 or BRCA-2 genes are at increased risk for breast and ovarian cancer. Based on current estimates, female carriers of BRCA-1 or BRCA-2 have a 50 to 80 percent chance of developing breast cancer and a 15 to 45 percent chance of developing ovarian cancer in their lifetime, usually at younger ages. Males who carry the gene also are at an increased risk of developing breast cancer.
Individuals with suspicious family histories of cancer may want to consider genetic testing. A computerized risk assessment may help better define the likelihood of being a gene carrier. Although it is just a simple blood test, the process is anything but simple because of the many psychological, ethical, and societal issues. Because of all these possible factors, doctors recommend pre- and posttest counseling with a qualified genetic counselor. Doctors generally discuss testing when a patient has two or more other family members (such as a mother, sister, aunt, and/or grandmother) from the same bloodline with a history of premenopausal breast cancer and/or ovarian cancer or male breast cancer. Doctors are also more concerned if they hear that family members have had breast cancer in both breasts.
A woman with a personal history of breast cancer and who is found to have inherited a mutation in BRCA-1 or BRCA-2 does not appear to be at higher risk of recurrence in that breast. However, she is at higher risk of developing a new, unrelated second cancer in the same or opposite breast. Some women may approach treatment decisions differently because of this knowledge, thus they may consider genetic testing soon after being diagnosed with breast cancer. This may change what she and her doctors decide to do to prevent second cancers. Stage for stage, though, these women have the same chances for a cure as those patients who don’t carry a susceptibility gene.
Women who have inherited mutations in BRCA-1 or BRCA-2 but have not been diagnosed with cancer may want to consider strategies for prevention. These strategies include preventative surgery (prophylactic mastectomy or oophorectomy) or use of medications such as tamoxifen. They may also seek high-risk screening programs, available at many breast centers or cancer centers, for close surveillance and to help them access new strategies for prevention and early detection.