Screening for Breast Cancer - Introduction
The importance of detecting localized breast cancer was recognized in the mid-eighteenth century by Henri Francois LeDran, who proposed that breast cancer originated as a localized disease that subsequently spread via the lymphatics to the general circulation. According to Donegan, this pivotal concept established the idea that surgery, if performed early, offered the potential to cure breast cancer.
However, it was not until the early twentieth century that experimental work with x-rays by Salomon and others demonstrated the detection of occult breast disease, thereby establishing the potential for diagnosis before the earliest detection of a palpable mass. These important discoveries ushered in the technology and the public health impetus to screen for breast cancer.
Once the efficacy of breast cancer screening was confirmed by early results from the Health Insurance Plan of Greater New York randomized trial (HIP), more fundamental questions about organized screening began to be asked. Could mammography and clinical breast examination (CBE) achieve the same results at the community level as had been demonstrated in the HIP trial?
Would women and their doctors participate in regular screening for breast cancer? To answer these questions, the American Cancer Society (ACS) and the National Cancer Institute (NCI) cosponsored the Breast Cancer Detection Demonstration Project (BCDDP), which screened more than 280,000 women at 29 centers between 1973 and 1980.
Participation rates were high over the course of the study, and nearly one-half of all breast cancers were found by mammography alone. Furthermore, the distribution of stage at diagnosis was much more favorable among study participants compared with incident cases in the NCI’s Surveillance Epidemiology and End Results program during the same time period; overall long-term survival likewise has been better.
These results, in combination with the findings from the HIP study, were sufficiently persuasive to justify promotion of routine breast cancer screening, a public health initiative that continues to be a high priority. In addition to the HIP and BCDDP studies, seven additional randomized trials have contributed evidence related to screening for breast cancer with mammography.
There is widespread acceptance of the value of regular breast cancer screening as the single most important public health strategy to reduce mortality from breast cancer. In 1981, Illinois passed the first legislation that required insurance companies to address health insurance coverage for mammography as part of their health plans, and now nearly all states have legislation requiring that routine mammography be offered as part of a basic benefits package.
The Health Insurance Financing Administration (HCFA) now provides for annual mammography for all Medicare beneficiaries aged 40 and older and waives the Part B deductible. Surveys of physicians reveal support for the value of mammography for their patients, and the most recent survey results show that a majority of women aged 40 and older report having had a mammogram in the previous 2 years.
The control of breast cancer has historically relied entirely on successful treatment, which has been measurably improved by favorable shifts in stage at diagnosis brought about by screening as well as gains in treatment regimens. However, continued progress in our understanding of the epidemiology of breast cancer, and the recent results of the Breast Cancer Prevention trial showing a 49% reduction in breast cancer incidence among a higher-risk cohort of women who took tamoxifen, suggest that over time, primary prevention strategies will begin to provide a greater and more direct contribution to breast cancer control.
Yet, however encouraging, the overall potential for breast cancer prevention in average- and higher-risk women through either lifestyle modification or chemoprevention is uncertain at this time. For this reason, early detection and appropriate treatment will remain the cornerstones of the disease control strategy for the foreseeable future.
In this chapter, we discuss breast cancer screening in the context of basic screening principles, methodologic issues related to the evaluation of screening, the current evidence of screening efficacy, and practical and clinical aspects of modern breast cancer screening.
Robert A. Smith and Carl J. D’Orsi
R. A. Smith: Cancer Screening, Department of Cancer Control, American Cancer Society, Atlanta, Georgia
C. J. D’Orsi: Diagnostic Radiology, University of Massachusetts Memorial Medical Center, Worchester, Massachusetts