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Breast Cancer Information
Breast Cancer, malignant tumor in the glandular tissues of the breast. Such tumors, also called carcinomas, form when the processes that control normal cell growth break down, enabling a single abnormal cell to multiply at a rapid rate (see Cancer). Carcinomas, which tend to destroy an increasing proportion of normal breast tissue over time, may spread, or metastasize, to other parts of the body.
Mammogram Mammography is a special X-ray technique that is used to visualize soft tissues of the breast as a means for screening women for breast cancer. This mammogram shows calcification (dense white flecks) in a cancerous tumor. The nipple is to the left. The majority of breast cancers originate in the duct of the mammary, or milk-secreting, gland. The remainder arise in the glands themselves. Most tumors of either type show early evidence of invasive (malignant) behavior, but both may also exist in noninvasive forms.Photo Researchers, Inc./Kings College Hospital/Science Source
Breast cancer is the most common cancer in women, other than skin cancer. A major health problem in many parts of the world, it is especially prevalent in developed countries. As a result of large-scale screening of women considered at higher risk, a greater number of breast cancers have been discovered and treated in recent years, even in cases where the women experienced no symptoms. The American Cancer Society (ACS) estimates that in the United States about 203,500 new cases are diagnosed and about 40,000 women die each year from cancer originating in the breast. One in 8 American women who live to age 85 will develop this illness at some time during her life. According to the Canadian Cancer Society, 19,000 new cases are diagnosed in Canada each year, and 5,300 Canadian women die from the disease annually. The rate of incidence increases with age, and women 75 years and older are at highest risk. Breast cancer can affect males, but the disease strikes women about 100 times as often as it does men.
II RISK FACTORS
Scientists do not understand exactly what causes breast cancer. Studies suggest that several categories of women are at increased risk for the disease: those with a long menstrual history (menstrual periods that started before age 12 and ended after age 50); those who never gave birth or who waited until after age 30 to have children; and those who have used birth control pills or hormone replacement therapy. Such risk factors, all of which relate to hormone-based life events, suggest that breast cancer is somehow affected by prolonged exposure to female sex hormones, such as estrogen.
Women with a history of breast cancer in the family are also at greater risk. About 5 percent of all breast cancers have been attributed to a mutated, or structurally altered, gene known as BRCA1. Mutations in a second gene, BRCA2, contribute significantly to the development of breast cancer in Jewish women of eastern and central European origin.
Breast cancer seems to be more common in women who do not exercise regularly and are unable to maintain a healthy body weight. Alcohol has also been linked to increased risk for breast cancer. The ACS reports that women who drink two to five alcoholic beverages a day have about 1.5 times the risk of developing breast cancer than women who drink no alcohol.
Studies also indicate that women who routinely work night shifts may increase their risk of developing breast cancer by as much as 60 percent. Scientists theorize that the body’s production of melatonin (a hormone that, among other tasks, regulates sex hormones) peaks during nighttime darkness. Exposure to bright light during the night decreases melatonin production, which may in turn increase estrogen levels. These studies may account for why women in industrialized nations, who are exposed to more artificial light at night, have a greater risk of breast cancer than those in developing nations.
III SYMPTOMS AND DIAGNOSIS
Woman Receiving a Mammogram Physicians use specialized X-ray images of the breast called mammograms to detect tumors and other breast abnormalities before they can be felt as lumps. Mammograms detect many breast tumors in their early stages, before they have a chance to spread to other parts of the body. Because catching and treating a cancerous breast tumor early significantly improves a woman’s chance of survival, the American Cancer Society recommends that women age 40 and over have an annual screening mammogram.Tony Stone Images/Charles Thatcher
Three-quarters of all breast cancer patients seem to have no factors that place them at increased risk for breast cancer, indicating that not all risk factors are understood. As a result, doctors recommend that every woman should have an annual breast examination performed by a health professional, and she should perform a breast self-examination monthly. A woman who finds a lump in her breast should report it to her doctor immediately.
However, a lump in the breast is no sure sign of cancer. Every breast is lumpy to some degree and the lumpiness becomes more pronounced shortly before menstruation as breasts naturally enlarge. Furthermore, several disorders of the breast produce growths that may be mistaken for carcinomas. Such noncancerous growths include cysts, which are fluid-filled sacs, and fibroadenomas, which are thickenings of the breast tissues that produce milk.
X-ray examination of the breasts, a technique called mammography, can increase the odds for successful treatment by detecting tumors in an early stage, before they are large enough to be felt. Although studies provide conflicting results about the effectiveness of mammography in reducing breast cancer deaths, the ACS recommends that women over age 40 should have a mammogram every year. A mammogram cannot distinguish a benign tumor from a malignant tumor. The only way to make a positive diagnosis on a suspect lump in the breast is by having a biopsy, a minor surgical procedure in which the lump or part of the lump is removed and examined under a microscope for cancer cells.
If cancer is found in the breast, doctors try to determine if malignant cells have metastasized beyond the breast and surrounding tissues, which may lead to serious, often fatal, complications. The most common sites of metastasis in breast cancer patients are the lymph nodes located in the armpit. The presence or absence of cancer cells in the lymph nodes helps physicians determine how far the cancer has advanced. Doctors usually remove several underarm lymph nodes to determine if they are cancerous. This surgical procedure may produce lymphedema, a painful swelling of the arm due to fluid accumulation, and it may place a woman at increased risk for infection. In a new procedure called sentinel-node biopsy, doctors use a less-invasive method to identify and remove a sentinel node, a single lymph node to which cancer cells from the breast travel first. If the sentinel node does not contain cancer cells, the cancer has not spread beyond the breast and the woman is saved more extensive surgery.
Treatment of breast cancer depends on a woman’s age and health as well as the type, extent, and location of the tumor, and if the cancer has remained in the breast or has spread to other parts of the body. Treatment may include surgery, radiation, chemotherapy, hormone therapy, or a combination of treatments.
Most women with breast cancer will have some type of surgery. If only the lump and some surrounding breast tissue are removed, leaving most of the breast intact, the procedure is called a partial mastectomy, or lumpectomy. In a simple mastectomy, only the affected breast is removed. A modified radical mastectomy involves the removal of the entire breast and some of the underarm lymph nodes near the breast. Surgery that removes the breast, lymph nodes, and chest wall muscles under the breast is called a radical mastectomy.
For women who have had a partial mastectomy, doctors generally recommend radiation therapy. Radiation therapy uses high-energy rays or particles that destroy cancer cells that may remain in the breast, chest wall, or underarm area after surgery (see Radiology: Therapeutic Radiology).
Studies have shown that lumpectomy combined with radiation therapy is as effective as mastectomy in treating early-stage breast cancer—there is no difference in survival rates of women treated with either of these two approaches. For this reason many women choose the less-invasive method of lumpectomy followed by radiation to avoid the complete removal of a breast. But this breast-conserving treatment is not an option for all women with breast cancer, including those who have already had radiation therapy to the affected breast or those with two or more areas of cancer in the same breast that are too far apart to be removed through one surgical incision. In some cases mastectomy is a woman’s only choice. Many women choose to have breast reconstruction surgery right after a mastectomy to restore the breast’s appearance.
If doctors find that cancer cells have spread to lymph nodes, then they will recommend chemotherapy. In chemotherapy, a patient receives cancer-fighting drugs that travel through the body to slow the growth of cancer cells or kill them. Even if no cancer cells are found in tissues other than the breast, chemotherapy may be given in addition to surgery to reduce the risk that breast cancer will recur. It also may be used as the primary treatment for women with more advanced cases of breast cancer to reduce the size of the tumor for more manageable surgical removal. In these cases, high doses of chemotherapy kill cancer cells, but they also kill stem cells, blood-producing cells in the bone marrow. Some women in advanced stages of breast cancer may undergo chemotherapy followed by a bone-marrow transplant to restore healthy stem cells, although it is not yet clear whether this procedure helps prolong a woman’s survival.
Hormone therapy exploits some of the chemicals the body naturally produces. For example, some breast cancer cells thrive on the hormone estrogen, which is produced in the ovaries. Hormone therapy slows the growth of such cells by preventing them from using estrogen. One of the drugs employed in hormone therapy is tamoxifen, which can prevent breast cancer from recurring in a majority of women. Tamoxifen has also been shown to reduce the risk of breast cancer in women who carry a mutation in the BRCA2 gene, which produces tumors that require estrogen to grow. Tamoxifen does not reduce the risk in women who carry the BRCA1 gene, which produces tumors not affected by estrogen. Tamoxifen may also prevent new cancers from forming in the other breast. Tamoxifen’s chemical cousin, raloxifene, has shown similar results in preliminary studies. The most radical forms of hormone therapy are the removal of the ovaries by surgery or the virtual destruction of the ovaries by radiation treatments to prevent these organs from secreting estrogen.
While tamoxifen blocks estrogen from being used by breast-cancer cells to stimulate further growth, other types of drugs under investigation reduce the amount of estrogen available in the body of postmenopausal women. At menopause (the permanent cessation of menstruation) the ovaries cease to produce estrogen, but estrogen production continues in other tissues, including breast tissue. Scientists are exploring the effectiveness of aromatase inhibitors and aromatase inactivators—drugs that suppress estrogen production by preventing the final step in estrogen synthesis. Studies show that aromatase inhibitors and inactivators, taken in combination with tamoxifen, reduce the size of breast tumors. Smaller tumor size means that patients can undergo less radical surgery.
Another drug recently approved for treating breast cancer is a monoclonal antibody called trastuzumab, marketed under the brand name Herceptin. This drug targets cells that overproduce HER-2, a protein implicated in about one-third of all breast cancer cases. Herceptin suppresses rapid tumor growth, enhancing the effectiveness of chemotherapy.
Women with a family history of breast cancer may choose to undergo genetic testing to determine if they carry mutated forms of the BRCA1 or BRCA2 genes. There is no way to know for sure if a woman who carries these genes will develop breast cancer, but statistics show that about 50 to 60 percent of women with these mutations will develop the disease by the age of 70. Although there is no sure-fire way to prevent breast cancer, women who test positively for these genes may elect to take precautions that may lower their risk of developing the disease. For example, they may decrease the level of fat and alcohol in their diets and eat more fruits and vegetables—foods that have been shown to decrease an individual’s risk of developing most types of cancer. Recent studies show that in women who are at very high risk for breast cancer, prophylactic mastectomies significantly lower this risk. In this procedure, surgeons remove both breasts before any signs of breast cancer are detected to remove the vulnerable tissue before cancer can take hold.
The five-year survival rate (a measure used to monitor persons who are living five years after diagnosis of cancer) for American women diagnosed with localized breast cancer increased from 72 percent in the 1940s to 96 percent in the late 1990s. If the cancer has spread to adjacent tissue, the five-year survival rate falls to 78 percent. For women who have been treated for breast cancer, the outlook is increasingly optimistic, especially with regular follow-up examinations by a physician and frequent breast self-examination.