The full potential of breast cancer screening use to reduce mortality has not yet been realized in the United States

Objective. Breast cancer mortality has been declining in European countries and the United States since the early 1990s. Based on breast cancer screening programs in western European countries, the reduction in mortality results from a predictable pattern of increasing early-stage and subsequent declining incidence of late-stage cancers. The purpose of this study was to determine whether changes in the incidence of early-stage and late-stage breast cancers has occurred in the United States to suggest that a reduction in breast cancer mortality is the result of screening. Method. The analyses are based on women 50-69 years of age using 1990-1998 Surveillance, Epidemiology, and End Results data. Five indicators that are precursors to reductions in mortality are described: in situ breast cancer, T1 tumors (<2 cm), stage II-IV tumors, lymph node-positive cancers, and locally advanced breast cancers (LABC). Results. The rate of in situ tumors increased from 37.8 to 67.0 per 100,000 population and that of T1 tumors increased from 143.5 to 163.5 per 100,000 population during 1990-1998. The rates of stage II-IV tumors, lymph node-positive cancers, and LABC remained unchanged at about 120 per 100,000, 76 per 100,000, and 17 per 100,000 population, respectively. Conclusions. Although there has been an increase in early-stage breast cancers (in situ and T1 tumors), the prerequisite decline in late-stage cancers has not yet occurred in the United States - a pattern that was observed in European studies. Possible explanations include the lack of widespread mammography use during the 1980s and, therefore, insufficient elapsed time since mammography use has become more widespread.