Tasas

The

n e w e ng l a n d j o u r na l

of

m e dic i n e

spe ci a l r ep or t

The Decrease in Breast-Cancer Incidence in 2003 in the United States
Peter M. Ravdin, Ph.D., M.D., Kathleen A. Cronin, Ph.D., Nadia Howlader, M.S., Christine D. Berg, M.D., Rowan T. Chlebowski, M.D., Ph.D., Eric J. Feuer, Ph.D., Brenda K. Edwards, Ph.D., and Donald A. Berry, Ph.D. age-adjusted incidence ofbreast cancer by an average of about 0.5% per year, a rise that was particularly evident among women who were 50 years of age or older2 (Fig. 1). Changes in reproductive factors, in the use of menopausal hormonereplacement therapy, in mammographic screening, in environmental exposures, and in diet have all been proposed to explain the trend. Of these factors, only the use of hormone-replacementtherapy changed substantially between 2002 and 2003. In this report, we provide additional data from 2004 that show little change in breast-cancer incidence between 2003 and 2004. A comparison of incidence rates in 2001 with those in 2004 (omitting the years in which the incidence was in the process of changing) showed that the decrease in annual age-adjusted incidence was 8.6% (95% CI, 6.8 to 10.4).The decrease in breast-cancer incidence began in mid-2002 and occurred shortly after the highly publicized series of reports from the randomized trial of the Women’s Health Initiative, which reported a significant increase in the risks of coronary heart disease and breast cancer associated with the use of estrogen–progestin combination therapy.3 By the end of 2002, the use of hormonereplacementtherapy had decreased by 38% in the United States, with approximately 20 million fewer prescriptions written in 2003 than in 2002.4,5 The analyses we report here used information from the SEER Program of the National Cancer Institute (NCI) collected from nine cancer registries reporting on 9% of the U.S. population. Trends in the incidence of female breast cancer were age-adjusted to the standardpopulation in the year 2000 and were adjusted for reporting delays. Joinpoint (version 3.0) statistical software (http://srab.cancer.gov/joinpoint/) was used for fit-

summar y
An initial analysis of data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) registries shows that the age-adjusted incidence rate of breast cancer in women in the United States fellsharply (by 6.7%) in 2003, as compared with the rate in 2002. Data from 2004 showed a leveling off relative to the 2003 rate, with little additional decrease. Regression analysis showed that the decrease began in mid-2002 and had begun to level off by mid-2003. A comparison of incidence rates in 2001 with those in 2004 (omitting the years in which the incidence was changing) showed that thedecrease in annual age-adjusted incidence was 8.6% (95% confidence interval [CI], 6.8 to 10.4). The decrease was evident only in women who were 50 years of age or older and was more evident in cancers that were estrogen-receptor–positive than in those that were estrogen-receptor–negative. The decrease in breastcancer incidence seems to be temporally related to the first report of the Women’s HealthInitiative and the ensuing drop in the use of hormone-replacement therapy among postmenopausal women in the United States. The contributions of other causes to the change in incidence seem less likely to have played a major role but have not been excluded. Major changes in cancer incidence and death rates, as detected in cancer-registry data, provide unique opportunities to examine questions relatedto the cause, prevention, detection, and treatment of cancer. In a preliminary report, we suggested that such a major change in breast-cancer incidence occurred in 2003 in the United States.1 In contrast, the 1990s saw an increase in the annual
1670

n engl j med 356;16

www.nejm.org

april 19, 2007

Downloaded from www.nejm.org on May 2, 2007 . For personal use only. No other uses...