A generational increase in the incidence of advanced breast cancer for women ages 25 to 39 is small but statistically significant, according to a study.
In background information for the study, which appears in the Feb. 27 issue of the Journal of the American Medical Association, researchers noted that breast cancer is the most common malignant tumor in females ages 15 to 39 and accounts for 14% of all cancer in men and women in that age range. In 2008, a womans individual risk of developing breast cancer by age 40 was 1 in 173 on average.
Young women with breast cancer tend to experience more aggressive disease than older women and have lower survival rates, the authors wrote. Given the effect of the disease in young people and a clinical impression that more young women are being diagnosed with advanced disease, we reviewed the national trends in breast cancer incidence in the United States.
Rebecca H. Johnson, MD, of Seattle Childrens Hospital and the University of Washington, Seattle, and colleagues conducted a study in which breast cancer incidence, incidence trends, and survival rates as a function of age and extent of disease at diagnosis were obtained from three U.S. National Cancer Institute Surveillance, Epidemiology, and End Results registries. These registries provide data spanning 1973-2009, 1992-2009 and 2000-09. SEER defines localized breast cancer as disease confined to the breast, regional as contiguous and adjacent organ spread (such as lymph nodes and chest wall), and distant as remote metastases (bone, brain, lung, etc).
Since 1976, there has been a steady increase in the incidence of distant disease breast cancer in 25- to 39-year-old women, from 1.53 per 100,000 in 1976 to 2.90 per 100,000 in 2009. The researchers noted this is an absolute difference of 1.37 per 100,000, representing an average compounded increase of 2.07% per year over the 34-year interval a relatively small increase, but the trend shows no evidence for abatement and may indicate increasing epidemiologic and clinical significance.
The trajectory of the incidence trend predicts that an increasing number of young women in the United States will present with metastatic breast cancer in an age group that already has the worst prognosis, no recommended routine screening practice, the least health insurance and the most potential years of life, the authors added.
The researchers also found the rate of increasing incidence of distant disease was inversely proportional to age at diagnosis. The greatest increase occurred in 25- to 34-year-old women. Progressively smaller increases occurred in older women by 5-year age intervals and no statistically significant incidence increase occurred in any group 55 years or older.
The authors noted that for women ages 25 to 39, the incidence of distant disease increased in all races and ethnicities assessed since at least 1992, when race/ethnicity became available in the SEER database. These increases occurred in both metropolitan and nonmetropolitan areas, and were statistically significant in African-American and non-Hispanic white populations.
Incidence for women with estrogen receptor-positive subtypes increased more than for women with estrogen receptor-negative subtypes.
Whatever the causes and likely there are more than one the evidence we observed for the increasing incidence of advanced breast cancer in young women will require corroboration and may be best confirmed by data from other countries, the authors wrote.
If verified, the increase is particularly concerning, because young age itself is an independent adverse prognostic factor for breast cancer, and the lowest five-year breast cancer survival rates as a function of age have been reported for 20- to 34-year-old women. The most recent national five-year survival for distant disease for 25- to 39-year-old women is only 31% according to SEER data, compared with a five-year survival rate of 87% for women with loco-regional breast cancer.
The study abstract is available at http://jama.jamanetwork.com/article.aspx?articleid=1656255.