Screening mammography is promoted as the key to the continued reduction in breast cancer mortality through early detection. A number of organizations, including the National Cancer Institute (NCI), the American Cancer Society (ACS), and the American College of Radiology , currently recommend routine screening every 1 to 2 years for women over age 40 (U.S. Preventive Services Task Force, 1996). Several randomized controlled studies have been undertaken in four countries to assess the value of screening mammography (reviewed by Moss [1999]  and Jatoi [1999]) (Table 1-2). Most of them demonstrated a substantial reduction in rates of death from breast cancer (about 25 to 30 percent) among women screened by mammography, and meta-analysis has confirmed a clear benefit of screening mammography for women over age 50 (Kerlikowske et al.,  1995;  Kerlikowske,  1997).  (A recent review published in The Lancet criticized six of the eight trials for methodological inadequacies in randomization procedures that led to baseline imbalances and for determining the cause of death without blinding [Gotzsche and Olsen, 2000].

TABLE 1-2 Results of Randomized Clinical Trials of Screening Mammography
NOTE: RR, relative risk (a value less than 1 indicates fewer breast cancer deaths among screened women); CI, confidence interval, NBSS, national breast screening study.
^a Compared mammography plus CBE with no screening.
^b Compared mammography plus CBE with CBE alone (all others compared mammography with no screening).
SOURCES: adapted from Jatoi (1999), Kerlikowske et al. (1995), and Moss (1999).

The authors concluded that because the two studies without these problems showed no reduction in mortality rates for the screened groups, screening for breast cancer by mammography is unjustified. An accompanying editorial and several letters to the editor rebutted the review, pointing out that the baseline differences were very small, that many other criteria are important for the assessment of screening trials, and that one trial did not assess screening but, rather, compared two different methods of screening.)  The reported reduction in breast cancer mortality among women aged 40-49 appears to be less than that of older women, with a longer time period between initiation of routine screening and observation of reduced mortality. As a result, the value of screening women younger than age 50 is still controversial, as will be discussed later in this section.

There are now a variety of venues for mammography breast cancer screening, including doctors’ offices, private radiology practices, hospital radiology departments, imaging centers, breast clinics, and mobile mammography vans. Because the effectiveness of screening mammography is dependent on the quality of the facilities and personnel,  a federal law requires all mammography facilities to be certified by FDA. The intent of the Mammography Quality Standards Act (MQSA)  was to ensure that all facilities meet federal standards for equipment, personnel, and practices.

TABLE 1-2 Results of Randomized Clinical Trials of Screening Mammography

NOTE: RR, relative risk (a value less than 1 indicates fewer breast cancer deaths among screened women); CI, confidence interval, NBSS, national breast screening study.
^a Compared mammography plus CBE with no screening.
^b Compared mammography plus CBE with CBE alone (all others compared mammography with no screening).
SOURCES: adapted from Jatoi (1999), Kerlikowske et al. (1995), and Moss (1999).

TABLE 1-3  Mammographic Diagnostic Assessment Categories (Breast Imaging Reporting and Data System) – BIRADS
SOURCE:  American College of Radiology:  Breast Imaging Reporting and Data System (BIRADS).  Reston, Virginia, American College of Radiology, 1998.

Since its inception,  the quality of mammograms has improved (Suleiman et al., 1999; U.S. General Accounting Office, 1998a,b; Wagner, 1999). However, mammography is the only medical examination that is federally regulated in this way, and the regulations substantially increase the cost of performing mammography (Inman, 1998; Wagner, 1999).