Incidence of breast cancer in the United States: current and future trends

Abstract

Background: The incidence of breast cancer increased in the United States until circa 2000 then decreased, mostly among women with estrogen receptor (ER)-positive cancers. Time trends provide important clues for cancer etiology and prevention; however, the observed trends of ER-positive and ER-negative breast cancers can be biased by missing ER data.

Methods: We developed a simple imputation method to correct invasive female breast cancer incidence for missing or unknown ER expression, using nationally representative data from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program during 1980-2008, including 588,720 invasive female breast cancer patients with 471,336,233 woman-years of follow-up. Corrected rates of ER-positive and ER-negative breast cancers were used to calculate age-standardized incidence rates, estimated annual percentage changes, and projections derived from age-period-cohort models.

Results: The recent decrease in the incidence of breast cancer overall stabilized near 200 per 100,000 woman-years by 2007-2008, reflecting a transient decrease in ER-positive cancers and a steady decrease in ER-negative cancers. The projected incidence rate for breast cancer overall through the year 2016 was similar to the incidence rate during 2007-2008. In contrast, rates of ER-positive breast cancers were projected to increase 5.3% (95% confidence interval = 5.2% to 5.4%), whereas rates of ER-negative breast cancers were projected to decrease 11.4% (95% confidence interval = 11.3% to 11.6%) during 2009-2016.

Conclusion: Recent changes in breast cancer incidence overall reflect the superimposition of divergent trends in ER-positive and ER-negative cancers. If current trends continue, the incidence of ER-positive breast cancers will increase, the incidence of ER-negative breast cancers will continue to decrease, and the incidence of breast cancer overall will remain similar to its current level.

Figure 1

Observed and corrected rates of estrogen receptor (ER)–positive and ER-negative invasive female breast cancer in the United States. Data are from the US National Cancer Institute’s Surveillance, Epidemiology, and End Results 13 Registries Database for cancers diagnosed between 1992 and 2008 (5). A) The proportion of all cancers with unknown ER data is given by calendar year of diagnosis with corresponding 95% confidence intervals (dashed lines). B) The proportion of all breast cancers with known ER status and an ER-negative test is given by age at diagnosis with corresponding 95% confidence intervals (dashed lines). C) Observed and imputed incidence rates of breast cancer by ER-positive and ER-negative expression are shown. Incidence rates were age standardized to the 2000 US standard population by the direct method and expressed per 100 000 woman-years among women aged 30–84 years.

Figure 2

Incidence rates for breast cancer overall and imputed rates of estrogen receptor (ER)–positive and ER-negative breast cancers for early (1980–1991), contemporary (1992–2008), and future (2009–2016) periods. Incidence rates were age standardized to the year 2000 US standard population by the direct method and expressed per 100 000 woman-years among women aged 30–84 years, and 95% confidence intervals are shown (dashed lines). Projected breast cancer rates were obtained using age–period–cohort models.

Figure 3

Imputed incidence rates of breast cancer by age, estrogen receptor (ER) status, and race. The imputed incidence rates are shown for women A) aged 30–49 years, B) 50–84 years, and C) 30–84 years who were of non-Hispanic white or black race/ethnicity, and 95% confidence intervals (dashed lines) were calculated. NH = non-Hispanic.