More women are getting breast cancer, but no one yet knows all the reasons why. Some of the increase can be traced to better ways of recognizing cancer and detecting cancers in an early stage. The increase also may be the result of changes in the way we live-- postponing childbirth, taking replacement hormones and oral contraceptives, eating high-fat foods, or drinking more alcohol.
The encouraging news is that, more and more, breast cancer is being detected early, while the tumor is limited to the breast and very small. Currently, two-thirds of newly diagnosed breast cancers show no signs that the cancer has spread beyond the breast.
With prompt and appropriate treatment, the outlook for women with breast cancer is good. Moreover, a majority of women diagnosed with early stage breast cancer are candidates for treatment that saves the breast.
The Key : Early Detection
The key to finding breast cancer is early detection, and the key to early detection is screening: looking for cancer in women who have no symptoms of disease. The best available tool is a regular screening mammogram--x-ray of the breast--coupled with a clinical breast exam--by a doctor or nurse.
A mammogram is an x-ray of the breast. Cancers that are found on mammograms but that cannot be felt (nonpalpable cancers) usually are smaller than cancers that can be felt, and they are less likely to have spread.
Mammography is not foolproof. Some breast changes, including lumps that can be felt, do not show up on a mammogram. Changes can be especially difficult to spot in the dense, glandular breasts of younger women. This is why women of all ages should have their breasts examined every year by a physician or trained health professional.
Two Kinds of Mammography: Diagnostic and Screening
If a woman visits her doctor because of unusual breast changes such as a lump, pain, nipple thickening or discharge, or changes in breast size or shape, or has a suspicious screening mammogram, the doctor often asks her to have a diagnostic mammogram: an x-ray of the breast to help assess her symptoms. A diagnostic mammogram is a basic medical tool, and it is appropriate for women of any age.
This booklet discusses screening mammograms: x-rays that are used to look for breast changes in women who have no signs of breast cancer. (Even though the woman has no symptoms of breast disease, a diagnosis of breast cancer can begin with a doctor checking a screening mammogram.)
What Are the Benefits of Screening Mammography? High-quality mammography is the most effective tool now available to detect breast cancer early, before symptoms appear--often before a breast lump can even be felt. Regularly scheduled mammograms can decrease a woman's chance of dying from breast cancer. For some women, early detection may prevent the need to remove the entire breast or receive chemotherapy.
Who Benefits From Screening Mammography?
Studies done over the past 30 years clearly show that regular screening mammography significantly reduces the death rate from breast cancer in women over the age of 50. Recent results from studies show that regular mammography also reduces death rates from breast cancer in women who begin screening in their forties.
The effectiveness of mammography seems to increase as a woman ages, and the time it takes for benefits to emerge appears to take longer in younger women.
Who Is at Average Risk for Breast Cancer?
Simply being a woman and getting older puts you at average risk for developing breast cancer. The older you are, the greater your chance of getting breast cancer. No woman should consider herself too old to need regular screening mammograms.
Who Is at Higher Than Average Risk for Breast Cancer?
One or more of the following conditions place a woman at higher than average risk for breast cancer:
- personal history of a prior breast cancer
- evidence of a specific genetic change that increases susceptibility to breast cancer (See Gene Testing for Breast Cancer Susceptibility, page 18.)
- mother, sister, daughter, or two or more close relatives, such as cousins, with a history of breast cancer (especially if diagnosed at a young age)
- a diagnosis of a breast condition that may predispose a woman to breast cancer (i.e., atypical hyperplasia), or a history of two or more breast biopsies for benign breast disease (See Benign Breast Conditions and the Risk for Breast Cancer, page 26.)
Also playing a role in a heightened risk for breast cancer is breast density. Women ages 45 or older who have at least 75 percent dense tissue on a mammogram are at elevated risk. And a slight increase in the risk of breast cancer is associated with having a first birth at age 30 or older.
In addition, women who receive chest irradiation for conditions such as Hodgkin's disease at age 30 or younger remain at higher risk for breast cancer throughout their lives. These women require meticulous surveillance for breast cancer.
These factors that increase cancer risk--risk factors--do not by themselves cause cancer. Having one or more does not mean that you are certain or even likely to develop breast cancer. Even among women with no other risk factors except a strong family history--for example, both a mother and a sister or two sisters with early onset breast cancer--three-fourths will not develop the disease.
Clearly, there is much yet to be learned about what causes breast cancer.
What Are the Limitations of Screening Mammography?
Early detection by mammography does not guarantee that a woman's life will be saved. It may not help a woman who has a fast-growing cancer that has spread to other parts of her body before being detected. Also, about half of the women whose breast cancers are detected by mammography would not have died from cancer, even if they had waited until the lump could be felt, because their tumors are slow-growing and treatable.
False Negative Mammograms
Breasts of younger women contain many glands and ligaments. Because their breasts appear dense on mammograms, it is difficult to see tumors or to distinguish between normal and abnormal breast conditions. As a woman grows older, the glandular and fibrous tissues of her breasts gradually give way to less dense fatty tissues. Mammograms can then see into the breast tissue more easily to detect abnormal changes. About 25 percent of breast tumors are missed in women in their forties, compared to about 10 percent of women older than age 50. These are called false negatives. A normal mammogram in a woman with symptoms does not rule out breast cancer. Sometimes a clinical breast exam by a doctor or nurse can reveal a breast lump that is missed by a mammogram.
False Positive Mammograms
Between 5 and 10 percent of mammogram results are abnormal and require more testing (more mammograms, fine needle aspiration, ultrasound, or biopsy), and most of the followup tests confirm that no cancer was present. It is estimated that a woman who has yearly mammograms between ages 40 and 49 would have about a 30 percent chance of having a false positive mammogram at some point in that decade, and about a 7 to 8 percent chance of having a breast biopsy within the 10-year period. The estimate for false positive mammograms is about 25 percent for women ages 50 or older.
Increased Cases of Ductal Carcinoma In Situ (DCIS)
The increased use of screening mammography has increased the detection of small abnormal tissue growths confined to the milk ducts in the breast, called ductal carcinoma in situ (DCIS). Doctors don't know which, if any, cases of DCIS may become life threatening. Usually, the growth is removed surgically, and radiation treatment is often given.
How Mammograms Are Made
Mammography is a simple procedure. It uses a "dedicated" x-ray machine specifically designed for x-raying the breast and used only for that purpose (in contrast to machines used to take x-rays of the bones or other parts of the body). The standard screening exam includes two views of each breast, one from above and one angled from the side. A registered technologist places the breast between two flat plastic plates. The two plates are then pressed together. The idea is to flatten the breast as much as possible; spreading the tissue out makes any abnormal details easier to spot with a minimum of radiation. The technologist takes the x-ray, then repeats the procedure for the next view.
The pressure from the plates may be uncomfortable, or even somewhat painful. It helps to remember that each x-ray takes less than one minute--and it could save your life. It also helps to schedule mammography just after your period, when your breasts are least likely to be tender, or at the same time each year, if you no longer have your period.
Although some women are concerned about radiation exposure, the risk of any harm is extremely small. The doses of radiation used for mammography are very low and considered safe. The exact amount of radiation needed for a specific mammogram will depend on several factors. For instance, breasts that are large or dense will require higher doses to get a clear image. Federal mammography guidelines limit the radiation used for each exposure of the breast to 0.3 rad. (A "rad" is a unit of measurement that stands for radiation absorbed dose.) In practice, most mammograms deliver just a small fraction of this amount.
Specialized mammography facilities have experienced personnel as well as modern equipment that is custom designed for mammograms. The combination of good technology and expertise makes it possible to obtain good-quality x-ray images with very low doses of radiation.
Reading a Mammogram
The mammogram is first checked by the technologist and then read by a diagnostic radiologist, a doctor who specializes in interpreting x-rays.The radiologist looks for unusual shadows, masses, distortions, special patterns of tissue density, and differences between the two breasts (see photo). The shape of a mass can be important, too. A growth that is benign (noncancerous) such as a cyst, looks smooth and round and has a clearly defined edge. Breast cancer, in contrast, often has an irregular outline with finger-like extensions.
Many mammograms show nontransparent white specks. These are calcium deposits known as calcifications.
Macrocalcifications are coarse calcium deposits. They are often seen in both breasts. Macrocalcifications are most likely due to aging, old injuries, or inflammations. They usually are not signs of cancer. Macrocalcifications are usually associated with benign breast conditions; many clusters of macrocalcifications in one area may be an early sign of breast cancer.
Microcalcifications are tiny flecks of calcium found in an area of rapidly dividing cells. Clusters of numerous microcalcifications in one area can be a sign of ductal carcinoma in situ. (See DCIS, page 8.) About half of the cancers found by mammography are detected as clusters of microcalcifications.
Reporting the Results
The radiologist will report the findings from your mammogram directly to you or to your doctor, who will contact you with the results. If you need further tests or exams, your doctor will let you know. If you don't get a report, you should call and ask for the results.
Your mammograms are an important part of your health history. Being able to compare earlier mammograms with new ones helps your doctor evaluate areas that look suspicious. If you move, ask your radiologist for your films and hand-carry them to your new physician, so they can be kept with your file. Always make sure that the radiologist who reads your mammogram has the old films to use for comparison.
Mammograms and Breast Implants
A woman who has had breast implants should continue to have mammograms. (A woman who has had an implant following breast cancer surgery should ask her doctor whether a mammogram is still necessary.) However, the woman should inform the technologist and radiologist beforehand and make sure they are experienced in x-raying patients with breast implants.
Because silicone implants are not transparent on x-ray, they can block a clear view of the tissues behind them. This is especially true if the implant has been placed in front of, rather than beneath, the chest muscles.
Experienced technologists and radiologists know how to carefully compress the breasts to avoid rupturing the implant. They can also use special techniques to detect abnormalities, sliding the implant backward against the chest wall, and pulling the breast tissue over and in front of it. Interpreting the mammogram can also be difficult, especially if scar tissue has formed around the implant or if silicone has leaked into nearby breast tissues.
Choose a Mammography Facility
Many places--breast clinics, radiology departments of hospitals, mobile vans, private radiology practices, doctors' offices--offer high-quality mammography. Your doctor can arrange for a mammogram for you, or you can schedule the appointment yourself. You can call NCI's Cancer Information Service (1-800-4-CANCER) to find a mammography facility in your community.
All facilities must be certified by the Food and Drug Administration (FDA). (See Assuring High-Quality Mammography, page 13.) Staff of the facility are required to post the FDA certificate in a prominent place; if you don't see it, you should ask about certification. Without the FDA "seal of approval," it is now illegal for mammographic facilities to operate.
In addition to quality, another important consideration is cost. Most screening mammograms cost between $50 and $150. Most states now have laws requiring health insurance companies to reimburse all or part of the cost of screening mammograms; check with your insurance company. Medicare pays some of the cost for screening mammograms; check with your health care provider or call the Medicare Hotline (1-800-638-6833) for details.
Some health service agencies and some employers provide mammograms free or at low cost. Low cost does not mean low quality, however. A large government survey found that some of the facilities charging the lowest fees (often because they serve large numbers of women) were among the best in terms of complying with high-quality standards.
Your doctor, local health department, clinic, or chapter of the American Cancer Society, as well as NCI's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237), may be able to direct you to low-cost programs in your area.
Schedule a Regular Mammogram
Early detection of breast cancer is crucial for successful treatment, and regular screening mammography is currently the best tool for early detection. A 1993 survey by the National Center for Health Statistics found that 60 percent of all women ages 40 to 49 got a mammogram in the preceding 2 years, and 65 percent of women ages 50 to 64 had done so, but only 54 percent of women ages 65 and over had been screened during that time. It is clear that many women still do not get mammograms at regular intervals. Sadly, the women least likely to have regular exams include those at highest risk, women ages 60 and older.
The reason women most frequently give for having--or not having--a mammogram is whether or not the doctor suggested it. Although surveys show that more doctors routinely advise women about mammography, some fail to do so--because they forget, or because they assume that another doctor has done so. If your doctor doesn't suggest mammography, it will be up to you to raise the issue.
Other Techniques for Detecting Breast Cancer
Clinical Breast Exam
Most professional medical organizations recommend that a woman have periodic breast exams by a doctor or nurse along with getting regular screening mammograms. You may find it convenient to schedule a breast exam during your routine physical.
The examiner will look at your breasts while you are sitting and while you are lying down. You may be asked to raise your arms over your head or let them hang by your sides, or to press your hands against your hips. The examiner checks your breasts carefully for changes in the skin such as dimpling, scaling, or puckering; any discharge from the nipples; or any difference in appearance between the two breasts, including differences in size or shape. The next step is palpation: Using the pads of the fingers to feel for lumps, the examiner will systematically inspect the entire breast, the underarm, and the collarbone area, first on one side, then on the other.
A lump is generally the size of a pea before a skilled examiner can detect it. Lumps that are soft, round, and smooth tend not to be cancerous. An irregular, hard lump that feels firmly anchored within the breast tissue is more likely to be a cancer. However, these are general observations, not hard and fast rules.
A breast exam by a doctor or nurse can find some cancers missed by mammography, even very small ones. In addition to the skill and carefulness of the examiner, the success of a physical exam can be influenced by your monthly cycle and by the size of your breast, as well as by the size and location of the lump itself. Lumps are harder to find in a large breast.
Currently, mammography and breast exams by the doctor or nurse are the most common and useful techniques for finding breast cancer early. Other methods such as ultrasound may be helpful in clarifying the diagnosis for women who have suspicious breast changes. However, no other procedure has yet proven to be more effective than mammography for screening women with no symptoms; thus, most alternative methods of breast cancer detection are used primarily in medical research programs.
Ultrasound works by sending high-frequency sound waves into the breast. The pattern of echoes from these sound waves is converted into an image (sonogram) of the breast's interior. Ultrasound, which is painless and harmless, can distinguish between tumors that are solid and cysts, which are filled with fluid. Sonograms of the breast can also help radiologists to evaluate some lumps that can be felt but are hard to see on a mammogram, especially in the dense breasts of young women. Unlike mammography, ultrasound cannot detect the microcalcifications that sometimes indicate cancer, nor does it pick up small tumors.
Computed tomography, or CT scanning, uses a computer to organize and stack the information from multiple x-ray, cross-sectional views of a body's organ or area. The scans are made by having the source of an x-ray beam rotate around the patient. X-rays passing through the body are detected by sensors that pass the information to computers. Once processed, the information is displayed as an image on a video screen. CT can separate overlapping structures precisely and is sometimes helpful in locating breast abnormalities that are difficult to pinpoint with mammography or ultrasound--for instance, a tumor that is so close to the chest wall that it shows up in only one mammographic view.
Research on New Techniques
Several new techniques for imaging the breast are in the research stage. These include the use of magnetic resonance imaging (MRI) and positron emission tomography (PET scanning) to identify tissues that are abnormally active. MRI uses a large magnet to surround the patient along with radio frequencies and a computer to produce its images. PET scanning uses signals from radioactive traces to construct images. Laser beam scanning shines a powerful laser beam through the breast, while a special camera on the far side of the breast records the image.
Researchers are also striving to improve the detection power and diagnostic accuracy of mammography. Digital mammography is a technique for recording x-ray images in computer code, improving the detection of breast abnormalities. Computer-aided diagnosis, or CAD, uses special computer programs to scan mammographic images and alert radiologists to areas that look suspicious.
Finally, medical researchers are exploring the use of biological tests to detect tumor markers for breast cancer in blood, urine, or nipple aspirates.
Gene Testing for Breast Cancer Susceptibility
A breast cell progresses from normal to cancerous through a series of several distinct changes, each one controlled by a different gene or set of genes. Researchers have precisely located the BRCA1 and BRCA2 genes, key regions within a woman's chromosomes that control cell growth in breast tissue. A woman can inherit a mutation, an alteration in these genes that are essential for normal growth of breast cells, and this inherited change may put her at greater risk for eventually developing breast cancer. The recent identification of genetic changes in BRCA1 and BRCA2 makes a gene test possible.
Scientists estimate that alterations in the BRCA1 and BRCA2 genes may be responsible for about 5 to 10 percent of all the cases of breast cancer and for about 25 percent of the cases in women under the age of 30. BRCA1 mutation testing is primarily done in certain families whose members are inclined to develop breast cancer at an early age because of an inherited change. Special counseling programs occur before and after the testing to inform women about the possible consequences of receiving test results. It is hoped that these genetic tests may one day enable scientists to delay or prevent breast cancer in high-risk families. Positive results may enable careful watchfulness when appropriate; negative results may reassure those women in high-risk families who are at no greater than average risk for breast cancer.
Scientists at NCI and elsewhere believe that tests for alterations in genes that control growth in breast tissue and in other genes throughout the body require careful study to establish their appropriate use. In addition to BRCA1 and BRCA2, other genes and the proteins they control may be involved in breast cancer, and much more needs to be learned about the risk associated with particular genetic alterations. NCI supports research on the development of new genetic tests offered within a research setting and accompanied by genetic counseling. Counseling is important because test results must be properly understood, and a counselor can help persons with a positive test to handle possible discrimination in health or life insurance or in the workplace.
Source: National Cancer Institute, National Institutes of Health