American Cancer Society Guidelines for the Early Detection of Cancer Pt.3

SCREENING FOR BREAST CANCER :

ACS guidelines for breast cancer screening were last updated in 2003 (Table 1).4 Guidelines for the early detection of breast cancer in average risk women emphasize a process that begins after a woman is 20 years of age and consist of a combination of clinical breast examination, counseling to raise awareness of breast symptoms, and regular mammography beginning at age 40.

Between the ages of 20 to 39 years, women should undergo clinical breast examination every 3 years, and annually after age 40 years. This exam should take place during periodic health examinations, and provides an opportunity for health care professionals to update a woman’s family history of breast cancer, discuss the importance of early breast cancer detection, discuss the importance of regular mammography after age 40 years, and answer any questions women may have about their own risk, new early detection technologies, or other matters relating to breast disease. During these discussions, health care professionals can play a key role in raising awareness about the importance of recognizing symptoms of breast cancer and developing a heightened awareness about breast changes. Although the ACS no longer recommends that all women conduct regular breast self-examination (BSE), women should be informed about the potential benefits, limitations, and harms associated with BSE. Women may then choose to do BSE regularly, occasionally, or not at all. If a woman chooses to perform periodic BSE, she can receive instructions in the technique and/or have her performance reviewed. The guidelines update in 2003 placed a strong emphasis on the health care professional’s role in raising and regularly reinforcing awareness about breast cancer, early breast cancer detection, the importance of prompt reporting of any new symptoms, and most important, regular screening with mammography after age 40 years.

The ACS recommends that average-risk women should begin annual mammography at the age of 40 years. Women also should be informed about the scientific evidence demonstrating the value of detecting breast cancer before symptoms develop, and the importance of adhering to a schedule of regular mammograms. Benefits include a reduction in the risk of dying from breast cancer, less aggressive therapy, and a greater range of treatment options. Women also should be told about the limitations of mammography, specifically that mammography will not detect all breast cancers, and some breast cancers detected with mammography may still have poor prognosis. Further, women should be informed about the potential harms associated with mammographic screening, including false positives, biopsy for abnormalities that prove to be benign, and the short period of anxiety that naturally would accompany a period where there was uncertainty about the presence of a malignancy.

There is no set age at which mammography screening should be discontinued. Rather, the ACS recommends that the decision to stop mammography screening should be individualized considering the potential benefits and risks of screening in the context of overall health status and anticipated longevity. As long as a woman is in good health and would be a candidate for breast cancer treatment, she should continue to be screened with mammography.
The 2003 update of the breast cancer screening guidelines also addressed issues related to screening high-risk groups. Although there is not sufficient data to recommend a specific surveillance strategy for high-risk women, including women younger than age 40 years at significantly elevated risk, the ACS guidelines state that women at significantly increased risk for breast cancer may benefit from earlier initiation of screening, screening at shorter intervals, and the screening with additional modalities such as ultrasound or magnetic resonance imaging.4 As noted above, an update of these recommendations for high risk women is currently underway.
In 2005, the first results of the Digital Mammographic Imaging Screening Trial (DMIST) were published.7 The goal of the study was to determine in a large prospective study whether digital technology improved diagnostic accuracy over screen film mammography. The study was conducted at 33 sites in the United States and Canada, and included 49,528 asymptomatic women who presented for screening mammography. Women who agreed to be in the study were screened for breast cancer with both digital and screen-film mammography, and the exams were interpreted independently by two radiologists. As part of the study, women were expected to return for an additional screening examination after 1 year, or if they received an examination at a nonparticipating site, to have the results sent to the study coordinator.
Previous studies comparing digital mammography to screen-film mammography have not found digital mammography to be significantly more accurate than screen-film mammography in the detection of breast cancer, although there was some suggestion that digital mammography offered advantages over screen-film mammography by reducing the proportion of women recalled for further evaluation for positive findings.8 This advantage primarily is due to the ability of digital technology to manipulate the contrast in the image, as well as magnify areas that warranted closer evaluation. In the first report of findings from the trial, Pisano et al reported that there was no overall difference in diagnostic accuracy between digital mammography and screen-film mammography in the entire study group, but that the accuracy of digital mammography was significantly better than screen-film mammography in three distinct subgroups of women–women under the age of 50 years, premenopausal or peri-menopausal women, and women with heterogeneously dense or extremely dense breasts on mammography examination.8 The authors concluded that the apparent advantage evident with digital mammography likely was due to the ability to take the fullest advantage of the available contrast through digital manipulation in subgroups of women with a higher prevalence of dense breast tissue, a circumstance that makes mammography more challenging and is associated with a higher rate of errors.

While the apparent implication of these findings is that younger women and women with dense breast tissue should chose digital mammography over screen-film mammography, a change in policy related to the application to specific technologies to specific groups of women faces unique challenges. First, and perhaps foremost, is the fact that digital mammography is not widely available. Second, there likely will be interest in seeing if these results can be duplicated in additional studies. Third, given the relative scarcity of digital mammography at this time, further clarification of the advantages of digital over screen-film in these three groups would provide greater guidance to policy makers, which are the advantages of digital over screen-film attributable mostly to age, density, or both? However, given the unique advantages of digital mammography over screen-film mammography in terms of electronic storage, teleradiology, and image manipulation, these findings suggest that both the technology and the ability to effectively use the technology is maturing and, over time, that it offer an improvement over conventional imaging for some groups of women.