Major changes in breast cancer incidence in the United States over the period 2002 to 2004

Abstract

1533 Background: We have recently reported that a steep decrease in the incidence of breast cancer occurred in the United States in 2003 relative to 2002 (BCRT 100: S5, 2006). This decrease was most evident in patients older than 50, and largely occurred because of a decrease in the incidence of estrogen receptor positive breast cancer. This decrease occurred after the report in 2002 of the results of first of the Women s Health Initiative trials of postmenopausal hormone therapy (HT). This publication showed that use of a combined estrogen/progestin combination was associated with increased risk of breast cancer and heart disease and led to an immediate and substantial decrease in the use of HT in the US. Dramatic shifts in breast cancer incidence are unusual, and provide unique opportunities to test models that have been developed to explain trends in breast cancer incidence and mortality. We have been engaged in modeling trends in breast cancer incidence and mortality, in collaborative effects such as the Cancer Intervention and Surveillance Modeling Network (CISNET), to understand these and other processes (NEJM 353:1784–1792,2005). These models have practical implications for understanding the impact of changes in risk factors, use of prevention strategies, screening, and treatment of breast cancer. Methods: SEER public use incidence data from 1990 to the end of 2003 will be updated with information from the release in the spring of 2007 of incidence data for 2004. We will analyze the full data set through 2004 and report on the trends in incidence of breast cancer in the population as a whole and by subsets (such as age, estrogen receptor status, stage etc). We will also use the most recent and detailed data about HT use and screening mammography during this period as part of modeling. Results: We are awaiting SEER data from 2004 which will be released by April of 2007. Conclusions: Our first SEER based multi-year analysis of breast cancer incidence following the change in HT use in the US will be presented. Modeling of these trends in incidence will be discussed in the context of understanding the role of various contributors to the change in breast cancer incidence and what insights on the evolution of preclinical disease might be possible. No significant financial relationships to disclose.