IntroductionA recent abstract presented in a breast cancer symposium attributed the sharp decrease in female breast cancer incidence rates from 2002 to 2003 in the Surveillance, Epidemiology, and End Results (SEER) cancer registries of the United States to the reduced use of hormone replacement therapy since July 2002. However, this hypothesis does not explain the decrease that began in 1999 in the age-standardized incidence rate of invasive breast cancer in the nine oldest SEER cancer registry areas, although the trend through 2003 was not statistically significant. In this paper, we examine temporal trends in invasive and in situ female breast cancer by age, stage, tumor size, and estrogen receptor/progestin receptor (ER/PR) status in the nine oldest SEER cancer registry areas and consider the implication of these trends in relation to risk factors and screening.
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