Breast Cancer Incidence in the United States, 1976-2009

Breast cancer is the most common malignant tumor in the United States among adolescent and young adult women 15 to 39 years of age and accounts for 14% of all cancer among men and women in that age group. In 2008, the individual average risk of a woman in the United States developing breast cancer by the age of 40 was 1 in 173.

The disease tends to be more aggressive when diagnosed in young women compared with older women and survival rates are lower in young women. Researchers recently reviewed the national trends in breast cancer incidence in the United States and reported results of the review in JAMA [2013;309(8):800-805].

The researchers noted that evidence from the US National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database suggests that incidence of advanced breast cancer in young women is increasing; they designed this review to quantify this trend. The reviewers also sought to analyze the trend as a function of stage at diagnosis, race/ethnicity, residence, and hormone receptor status.

Data were obtained from SEER registries spanning 1973-2009, 1992-2009, and 2000-2009. SEER defines localized as disease confined to the breast, regional as contiguous and adjacent organ spread (lymph nodes, chest wall), and distant disease as remote metastases (bone, brain, lung, etc.).

The study’s primary outcome measure was breast cancer incidence in the United States.

The study found that the incidence of breast cancer in the United States increased in women 25 to 39 years of age from 1.53 (95% confidence interval [CI], 2.31-3.59) per 100,000 in 1976 to 2.90 (95% CI, 2.31-3.59) 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%-2.58%; P<.001) over the 34-year interval.

The greatest increase occurred in women 25 to 34 years of age, from 0.81 per 100,000 in 1976 to 2.14 per 100,000 in 2009 and at an annual percent change of 2.24 (95% CI, 1.38-3.12; P<.001). Progressively smaller increases occurred in older women by 5-year age intervals and no statistically significant incidence increase occurred in any group ≥55 years of age.

For women 25 to 39 years of age, the incidence of distant disease increased in all races/ethnicities assessed since at least 1992 (when race/ethnicity became available in the SEER database). From 1976 to 2009, in African-American and non-Hispanic white populations, the increases were statistically significant: 3.14 to 6.25 per 100,000 and 1.52 to 2.37 per 100,000 and APCs of 3.50 (95% CI, 1.42-5.58; P=.03) and 2.67 (95% CI, 1.29-4.06; P=.01), respectively. This increase occurred in both metropolitan and nonmetropolitan areas.

The incidence for women with estrogen receptor-positive subtypes increased more than for women with estrogen receptor-negative subtypes.

In summary, the reviewers stated, “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 25 to 39 years of age, without a corresponding increase in older women.”