Usefulness of Mammography for Breast Cancer Screening

There is little, if any, opposition to the practice of diagnostic mammography, probably because of the compelling clinical need for the information obtained. Many mammography examinations are performed for diagnostic purposes, and mammographic screening programs have also been widely implemented. There has been some opposition to screening in the past for a variety of reasons: (1) concern over a few published indications of a relatively unfavorable benefit/risk ratio, (2) concern about exposure to ionizing radiation, (3) concern about benefit in comparison to the number of false-positive mammograms, (4) the relatively high cost of mammography examinations and the cost of the biopsy procedures generated by screening mammography, and (5) the limited willingness of third-party payers and government agencies to reimburse adequately for screening procedures.

The introduction of the American College of Radiology (ACR) Mammography Accreditation Program (MAP) in 1987 and the passage of the federal Mammography Quality Standards Act of 1992 (MQSA, 1992), followed by its implementation in 1994, established requirements for consistent minimum standards for mammogra-phy programs throughout the United States.

Furthermore, the regulatory climate for mammography in the United States has changed significantly with the passage of MQSA (1992) and its subsequent revision in the Mammography Quality Standards Reauthorization Act of 1998 (MQSRA, 1998).1 Previously, mammography facilities were subject to a patchwork of state regulations and voluntary quality programs. With the implementation of MQSA (1992) by the U.S. Food and Drug Administration (FDA), a set of nationwide minimum quality standards now applies to all mammography facilities (Houn et al., 1995).

Under MQSA (1992), each mammography facility must be accredited by an FDA-approved accreditation body. Currently, the approved accreditation bodies are the ACR and the States of Iowa, Arkansas, California and Texas. Once accredited, a facility must be certified by FDA or by one of the states approved by FDA as a certifying agency.

In order to be accredited and certified, each mammography facility must meet quality standards promulgated by FDA in its regulations.2 These regulations address the facility's mammography equipment, its quality-assurance (QA) and quality-control (QC) program (including its mammography medical audit and a mechanism for addressing consumer complaints), its mammogra-phy personnel (interpreting physicians, radiologic technologists, and medical physicists), and its mammography reports. Issues related to the equipment and the QA and QC program (including the medical audit) are addressed in detail in this Report.

1Equipment standards for mammography are required by MQSA (1992) and MQSRA (1998). The Act can be found at http://www.fda.gov/ cdrh/mammography, click on "The Act" under "Regulations."

2Implementation of equipment standards and other criteria for mam-mography can be found at http://www.fda.gov/cdrh/mammography, click on "The Code of Federal Regulations" under "Regulations" and scroll down to "Section 900.12(b) Equipment."

Under MQSA (1992), all mammography personnel (interpreting physicians, radiologic technologists, medical physicists) are required to meet both initial and continuing requirements. The initial requirements address licensure and certification, initial training in mammography and initial experience. The continuing requirements address both education and experience.

Also under MQSA (1992), the medical reports describing the results of the mammogram are required to be sent to the referring physician (or to the patient if the patient has no referring physician) in a timely fashion. The report must include one of a required set of final assessment categories and a recommendation for additional imaging or biopsy, if indicated. MQSA (1992) also requires that a summary of the report written in lay language be sent to ALL patients.

In addition to the requirement that each facility be accredited and certified, each facility is also subject to an annual on-site inspection by FDA (or by a state radiation control agency acting for FDA) and is required to pay an inspection fee. If the results of the inspection show that the facility has failed to comply with the MQSA standards in significant ways, the facility is required to respond to FDA in writing about how the noncompliance has been corrected. If significant noncompliance with the MQSA (1992) requirements persists, the facility is subject to a variety of sanctions including suspension of its certificate or the imposition of civil financial penalties.

Compliance with the requirements of MQSA (1992) has been very high and several General Accounting Office studies (GAO, 1995; 1997a; 1997b) have indicated that MQSA (1992) has led to improvements in the quality of mammography in the United States (CDRH, 2002a).

An essential component in determining the efficacy of a screening program is an evaluation of benefits versus risk of harm. For mammography, the major risks to be addressed include radiation-induced breast cancer and the effects of false-positive and false-negative diagnoses. The balancing of potential benefit and harm has been, and continues to be, difficult because of the limited amount of available data. However, it is possible to estimate the recall rate and biopsy-requested rate of mammography screening and to estimate the breast cancer mortality reduction from screening. It is also possible to estimate the average radiation dose received per examination, and the level of risk of radiation-induced breast cancer. When these are considered in the context of the natural incidence of carcinoma of the breast, a benefit/risk ratio can be formulated. It must be emphasized that these are estimates based upon incomplete information, but that the level of reliability of the benefit estimates is probably as good as the data upon which the risk estimates are based. Because the doses are low and image quality has been greatly improved, it is believed that the benefit-risk ratio from screening with current state of the art mammogra-phy is likely to have increased substantially over that estimated in earlier studies.

Because of the substantial increase in mammography and mam-mographic screening and the anticipated further increase in utilization (CDRH, 2001), NCRP felt the need to update its previous report dealing with mammography, i.e., NCRP Report No. 85, Mammography—A User's Guide (NCRP, 1986), as well as provide more relevant technical and clinical information on the practice of mammography.

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