at regular intervals, whereas the large majority of women in the United States are referred by a health care provider or by themselves.
The British National Health Service pays for all screening mammograms in the United Kingdom, whereas mammograms in the United States are covered through a complex patchwork of medical payment systems that exclude millions of women.
The volume of mammographic interpretations required of radiologists to be eligible to read mammograms in the United States is about one-tenth that required in Britain.
The recommended interval for screening mammography is 12 months in the United States and 36 months in Britain.
Quality assurance standards concerning mammographic interpretation for the National Health Service Breast Screening Program are set nationally and are regularly monitored through a quality assurance network.
Although the threat of malpractice is frequently cited as an important reason for the difference in screening practices between the two countries, this is part of the larger context of the health care and can not be regulated through breast cancer screening programs. (Problems of malpractice in the United States are discussed later in this chapter in the section Breast Imagers Needed.)
Table 3-2 summarizes the different outcomes of the breast screening programs in the United States and Britain. The results in Table 3-2 are only valid for comparison within the same study which directly compares the two countries because of the similar methodology used in collecting the data; other studies with different methodology may result in different statistics. Overall, women in the United States are called back after screening mammograms about twice as often as women in Britain and significantly more of the surgical biopsies they undergo turn out to be negative. But this does not translate into improved rates of cancer detection, which are not significantly different between the countries. It could be argued that women in the United States are excessively subjected to unnecessary medical procedures.
Yet, the fact that breast cancer mortality rates in the United States are lower than they are in Britain must be considered. Although differences in treatment quality cannot be ruled out, there is a more immediate reason to expect higher breast cancer mortality in Britain. Breast cancers are detected at a later stage in Britain, and stage of detection is well established as a factor in survival. The three-fold difference in screening intervals between Britain and the United States is highly likely to be a significant contributor to the differences in mortality between the two countries. Longer screening intervals are associated with more false positives, as well as in increase in