Although monthly breast self-examination and periodic physical examination by a physician are important, most experts now agree that they are not enough. Mammography an X-ray examination of the breast is also an important part of early cancer detection.
After a certain age, regular screening by mammography X-ray examinations of the breast should be added to the routine. The American Cancer Society now recommends that all women undergo a base-line breast X-ray examination between the ages of thirty-five and forty. Mammography should be repeated every one or two years between the ages of forty and fifty, and every year after fifty.
Some tumors of the breast can be seen on X ray before they become detectable to the fingers of the physician or the woman herself. Recent studies have found that mammography can detect many of these cancers while they are still too small to be felt. Even for women who do not have breast lumps or other suspicious signs, regular mammography is advised after the age of forty to provide a basis of comparison. Mammography can guide the surgeon in performing a biopsy. However, when the physician feels that a biopsy is indicated to rule out the presence of cancer, a normal mammogram should not dissuade him or her from doing the biopsy.
Mammography should be performed by radiological technicians and interpreted by a radiologist skilled in reading mammograms. Usually two sets of pictures are taken of each breast: a view from above with the patient seated, and a side view while she lies on her back. The patient will probably be more comfortable in a two-piece outfit with a top that can be easily removed than in a dress, but no other preparation is needed.
Mammography in the detection of breast cancer is not new; indeed, the first record of mammography dates to 1913, when a German pathologist named Salomon used the technique. In the succeeding years, many radiologists both here and abroad have used the technique with varying results. In this country, particularly important contributions were made by Dr. Gershon-Cohen, a Philadelphia radiologist who first recognized the potential of using mammography to examine apparently well women to find unsuspected breast cancer, and by Dr. Egan, a Houston radiologist who developed improved techniques and excited the interest of the Public Health Service.
In the 1940s and 1950s, several researchers undertook studies to determine whether an annual breast examination was an effective screening tool for breast cancer. These studies had two major flaws: there were no control groups matched groups of women who did not undergo the examinations. And there was a large up to 30 percent incidence of interval cancers that appeared within a year of an apparently negative physical examination. Experts now agree that most of these interval cancers can be detected on mammography at the time of the original examination, a belief confirmed in the mid-1960s in a large study conducted by the Health Insurance Plan of Greater New York under a contract with the National Cancer Institute.
The H.I.P. study was designed to answer these questions: Would screening of apparently well women detect breast cancer in the early, curable stages? Would such an effort actually save lives? Finally, would adding mammography to physical examination increase breast-cancer detection?
After collecting data for more than thirteen years, several important findings have been reported.
One-third fewer women in the study group who had mammography and physical examinations died of breast cancer, compared to women in the control group who did not undergo regular screening.
Mammography is a highly valuable screening method. One third of all the cancers found were detected on X ray alone. In the course of eight years, only three of the forty-four women whose cancers were detected by mammography alone died.
The screening program detected cancer in its early stages. Four fifths of the cancers were still confined to the breast, greatly increasing chances of long-term survival or cure.
Findings of the H.I.P. study were instrumental in the 1968 establishment of the Guttman Breast Diagnostic Institute in New York, whose basic objective has been to develop an approach to breast-cancer screening that is practical, economical, and effective in detecting early breast cancer. Up to 50,000 women a year have been examined at the institute and hundreds of early breast cancers have been detected. In addition, improved mammographic techniques have been developed that are being used by other diagnostic facilities to make mammography safer and more accurate and economical.
The value of annual breast examinations in finding early breast cancer was conclusively shown in the Breast Cancer Detection Demonstration Project, a massive screening program undertaken in 1973 by the American Cancer Society and National Cancer Institute.
The study, known as the BCDDP, recruited some 280,000 women from throughout the United States to undergo annual breast examinations for five years, with an additional five-year followup by the twenty-nine participating BCDDP centers.
The women were taught breast self-examination and were encouraged to practice it monthly between their annual checkups, which included a physical examination and mammography. (In the early years of the study, thermography was also used during the annual examination, but was discontinued in 1977 because of high false negative and high false positive rates.)
In all, 4,443 breast cancers were detected among BCDDP participants. Normally, most suspicious breast lumps are discovered by the woman herself, but in the BCDDP, about 90 percent of the cancers were found by mammography, either alone (41.6 percent) or combined with physical examination (47.3 percent), during the annual examinations. A third of these were very small—less than one centimeter in diameter and 80 percent were localized, or confined to the breast, and therefore should have a five-year survival of more than 90 percent. Mammography proved to be one of the more important factors in detecting the very small cancers—a factor that was instrumental in revised recommendations calling for mammography every one or two years for women over forty and annually after the age of fifty.
Even though the value of mammography has been clearly demonstrated by the BCDDP and the H.I.P. study, adoption of the technique as a screening tool has been controversial. In 1975 the National Cancer Institute began to reevaluate the risks of repeated X-ray exposure in mammography compared with the benefits of early detection of breast cancers.
This study of the dangers of radiation was complicated by two facts: The carcinogenic results of radiation often take decades to appear and the machines used for mammography vary widely in the dose of radiation (measured in units called rads) per examination (four exposures—two of each breast). Even so, the media reported warnings by individual researchers who felt that mammography itself may increase the risk of breast cancer.
Understandably, large numbers of women became concerned by the reports and turned away from mammography as a screening procedure. Marked reduction in radiation exposure has discounted those early reports, and after much public debate and further study the National Cancer Institute issued guidelines stating that X-ray machines used for mammography should deliver no more than 1 rad of radiation per mammogram. The amount necessary for a good picture varies with the machine and with the size and density of the breast. The most modern machines use as little as 0.02 rad to the middle of each breast—considerably less than the amount of radiation delivered in a conventional chest X ray. Women should ask their physicians or radiologists how much radiation they will receive before undergoing mammography. If the answer is over 1 rad per exposure, it is advisable to find another radiologist with more up-to-date equipment.