What caused the decline in breast cancer incidence rates

1513 Background: Recently, a sharp 7% decline in breast cancer incidence rates among women over the age of 50 was noted in 2003. It has been speculated that this may be due to changes in mammographic screening or in the use of hormone replacement therapy (HRT). The purpose of this study is to elucidate the cause of the decline in breast cancer incidence rate. Methods: The National Health Interview Survey (NHIS) is a population-based personal interview survey conducted annually by the Centers of Disease Control. In 2000 and 2005, a cancer supplement was administered containing information regarding behaviors which may affect breast cancer incidence. These data were analyzed using SAS-callable SUDAAN software to determine trends in the use of mammography, HRT use, and chemoprevention over this period of time in women older than 50. Results: 7147 and 7396 women over 50 were surveyed in 2000 and 2005 respectively. There was a significant drop in the proportion of women reporting current use of HRT between 200...