Breast cancer is the most common type of cancer among American women. The American Cancer Society estimated that 203,500 new cases of breast cancer would develop in 2002, representing 31 percent of all cancers among women. Over her lifetime, a woman has a 10.6 percent chance of getting breast cancer. This lifetime risk does not apply to you as an individual; it represents the average risk for the population of American women. If you have certain risk factors for breast cancer, like a family history or a poor diet, this number underestimates your risk. If you have no risk factors at all for the disease, this lifetime risk overestimates your chances of getting breast cancer.
Sadly, more than 100 American women die every day from breast cancer. But the good news is that the death rate from breast cancer has decreased over the past 15 years. This is largely due to the fact that more and more women are having mammograms, allowing for earlier detection.
What Causes Breast Cancer?
Simply put, cancer is a disease in which abnormal cells grow out of control. When enough of these cells accumulate, a tumor forms. Finally, if the cancer cells are able
to break away from the tumor, they can circulate through the body and take up residence in another organ, a process called metastasis.
Every cell has a genetic blueprint, called DNA (deoxyribonucleic acid). The DNA of cells contains genes that program cell reproduction, growth and repair, affecting all body processes. Sometimes genes can become damaged and this damage can result in cancer. There are three ways in which your genes can become faulty:
1. A mutation can occur during normal cell division, such that the newly formed cell contains an abnormal gene. This can happen randomly or if the cell is exposed to some other agent.
2. Cells can be exposed to an environmental agent, a carcinogen that harms the DNA. For instance, cigarette smoke is a carcinogen that causes lung cancer.
3. Flawed genes can be inherited from your parents. In fact, very few cancers are actually the result of inherited genes.
Cancer is not explained by genetics alone. Experts agree that cancer is the result of an interaction between genes and environmental factors. For instance, you might have a mutated gene that predisposes you to breast cancer but, because you eat a low-fat diet with plenty of fruits and vegetables, the cancer may never express itself.
The breast is composed of fatty tissue and glands. Within this tissue are milk glands. Lobules are groups of individual milk-forming glands, and each lobule empties into ducts, small passageways that carry milk to the nipple. Breast cancer begins with a single cell that runs amok, usually in the lobule or duct. These are two areas where cells are rapidly dividing during the normal menstrual cycle. Estrogen and progesterone stimulate the breast cells to begin dividing each month, preparing the body for pregnancy. If conception does not occur, breast cell receptors receive a message to stop cell division. The process begins again the following month, and each month until menopause. With cell division regularly occurring for such a span of years, there is a greater chance for a genetic mutation to occur. While most breast cancers are not detected until after menopause, it is believed that they actually begin to develop in the premenopausal years.
Some cases of breast cancer are caused by inherited mutations in the genes BRCA1 and BRCA2. The gene BRCA1 is believed to account for 5 percent of breast cancers, specifically inherited early-onset breast cancer. Families that carry a faulty BRCA1 gene have a high incidence of both breast and ovarian cancer at a young age. Researchers are currently studying BRCA2 and BRCA3 genes.
Who’s at Risk?
The clearest risk factors for breast cancer are associated with hormonal and reproductive factors. It is thought that estrogen promotes the growth and development of mutated breast cells. It seems that the longer your breast tissue is exposed to your body’s circulating estrogen, the greater the risk for breast cancer.
1. Age Breast cancer is more common in women over 50 years of age. More than 75 percent of breast cancers occur in postmenopausal women. Increasing age also makes other risk factors discussed below more likely to occur. When two or more risk factors are combined, your risk is greater than with the one risk factor alone.
2. Previous breast cancer A history of breast cancer increases the odds that a woman will get breast cancer again, in the same and in the opposite breast.
3. Family history of breast cancer If you have a first-degree relative with breast cancer (a mother, sister or daughter), your risk is approximately doubled. There is an even greater risk if more than one close relative is affected, or if the cancer has occurred at a young age in a family member.
4. Age of first pregnancy Women who have children before 30 years of age have a lower risk of breast cancer. Women who have their first child after 30 have a higher risk, and women who never have children are at an even greater risk. Many experts believe that the important factor here is the amount of time between menarche (the age when you began menstruating) and first pregnancy. The theory is that the developing breast tissue is most sensitive to carcinogens during this time. Pregnancy hormones mature the breast cells and make them more resistant to carcinogens. It may be that these same pregnancy hormones stimulate mutated breast cells in a woman who has her first baby after 30 years of age.
5. Age of first period (menarche) Onset of your period at a young age—before 12 years of age—is associated with a slightly higher risk of breast cancer. It is believed that the longer breast tissue is exposed to endogenous estrogen (estrogen that’s made in your body), the greater the chance for cells to become cancerous.
6. Late menopause Women who menstruate for longer than 40 years have a slightly higher risk of breast cancer. Like early menarche, late menopause influences the amount of time breast cells are exposed to estrogen.
The list below describes factors that may play a role in the development of breast cancer, but they are less well understood:
1. Exposure to radiation Ionizing radiation from x-rays taken at a younger age may increase the risk for breast cancer later in life. However, experts feel exposure to radiation is probably a minor contributor to your overall risk.
2. Use of hormones Studies have failed to show an increased breast cancer risk in young women who take birth control pills. However, the same cannot be said for older women taking hormone replacement therapy (HRT). In July 2002 the Women’s Health Initiative (WHI), one of the largest-ever studies of HRT, was abruptly halted because of health risks. The researchers reported that the risk for breast cancer was 26 percent higher in the group of women taking combined HRT (estrogen plus progestin). On average there were about 38 cases of invasive breast cancer per 10,000 women, compared to 30 cases among women taking the placebo. For an individual woman, this translates into an increased risk of less than one tenth of one percent a year. Despite this small increase in risk, the study revealed that the longer a woman stayed on HRT, the more her risk increased. Clearly, the pros and cons of combined HRT need to be discussed with your physician.
3. Diet A growing body of research is finding a link between certain diet factors and the risk of breast cancer. Diet affects breast cancer development either by initiating cancer growth and causing a genetic mutation, or by promoting the growth of cancerous cells.
All American women aged 40 and older should have a screening mammogram every year, in combination with a physical exam of the breasts by a trained health
professional. A mammogram is a special x-ray of the breast that shows the location of a lump, its size and certain characteristics that may be suggestive of cancer. If a lump looks suspicious to your physician, further tests will be done to determine if it’s malignant and cancerous. Mammograms use very low doses of radiation and do not cause breast cancer, nor do they make an existing cancer worse. A mammogram is a very important screening tool that can catch breast cancer early and lead to a significant improvement in survival.
It is generally accepted that mammograms in women over 50 years of age save lives, but this is less certain in women aged 40 to 49 years. Currently some health professionals do not recommend routine mammograms for this age group, based on results from the Canadian National Breast Screening Study. In this ten-year study of 25,000 women aged 40 to 49 years, there was no difference in breast cancer death rates between women screened and women who were not screened.1
The breast self-exam is an important way for you to detect physical changes in your breasts. By the age of 20, all women should routinely perform monthly breast selfexams. Use the pads of your fingers to examine the tissue in your breasts and in your armpits. (Go to www.cancer.org for a step-by-step guide to breast self-examination.) Breast self-exams should be practiced at the same time each month. Be sure to also look carefully at your breast for any noticeable physical changes, such as a lump in the breast or underarm area, unusual breast swelling, change in color or texture of skin on the breast, blood leakage from the nipple or inversion of the nipple. Any of these changes should prompt a visit to your family doctor.
Preventing Breast Cancer
When it comes to breast cancer, dietary factors such as fat, alcohol, fiber, fruits and vegetables have all been well studied. Below, I list nutrition recommendations based on our current body of scientific evidence. Some of these strategies have strong research to support their adoption; others have evidence to suggest that they may be helpful. While scientists are still learning the role of nutrition in the risk of breast cancer, making these dietary changes will improve your overall well-being, not to mention possibly lowering your chances of getting breast cancer.