Importance: Evidence from the US National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database suggests that the incidence of advanced breast cancer in young women is increasing.
Objective: To quantify this trend and analyze it as a function of stage at diagnosis, race/ethnicity, residence, and hormone receptor status.
Design, setting, and patients: Breast cancer incidence, incidence trends, and survival rates as a function of age and extent of disease at diagnosis were obtained from 3 SEER registries that provide data spanning 1973-2009, 1992-2009, and 2000-2009. SEER defines localized as disease confined to the breast, regional to contiguous and adjacent organ spread (eg, lymph nodes, chest wall), and distant disease to remote metastases (bone, brain, lung, etc).
Main outcome measure: Breast cancer incidence trends in the United States.
Results: In the United States, the incidence of breast cancer with distant involvement at diagnosis increased in 25- to 39-year-old women from 1.53 (95% CI, 1.01 to 2.21) per 100,000 in 1976 to 2.90 (95% CI, 2.31 to 3.59) per 100,000 in 2009. This is an absolute difference of 1.37 per 100,000, representing an average compounded increase of 2.07% per year (95% CI, 1.57% to 2.58%; P < .001) over the 34-year interval. No other age group or extent-of-disease subgroup of the same age range had a similar increase. For 25- to 39-year-olds, there was an increased incidence in distant disease among all races and ethnicities evaluated, especially non-Hispanic white and African American, and this occurred in both metropolitan and nonmetropolitan areas. Incidence for women with estrogen receptor-positive subtypes increased more than for women with estrogen receptor-negative subtypes.
Conclusion and relevance: Based on SEER data, there was a small but statistically significant increase in the incidence of breast cancer with distant involvement in the United States between 1976 and 2009 for women aged 25 to 39 years, without a corresponding increase in older women.