More young women ages 25 to 39 are being diagnosed with aggressive, more advance forms of breast cancer, and they have lower survival rates, an analysis of breast cancer trends in the U.S. found.
Breast cancer is the most common malignant tumor in adolescent and young adult women ages 15 to 39, accounting for 14% of all cancer in men and women in the age group. The individual average risk of a woman developing breast cancer in the U.S. was 1 in 173 by the age of 40 years when assessed in 2008.
To analyze the trend, researchers reviewed data from three SEER registries for the years 1973-2009, 1992-2009, and 2000-2009 to review localized disease confined to the breast, regional diseases that spread to contiguous and adjacent organs such as the lymph nodes or chest wall, and distant disease that metastasized to bones, the brain, or lungs, for example.
Results appeared in the Feb. 27 issue of JAMA.
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 note that this is an absolute difference of 1.37 per 100,000, representing an average compounded increase of 2.07% (95% confidence interval, 1.57% to 2.58%) per year over the 34-year interval.
"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 wrote.
Also, the rate of increasing incidence of distant disease was inversely proportional to age at diagnosis. While 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 increases were seen in all races, in urban and rural areas, and were statistically significant in black and non-Hispanic white populations. Incidence for women with estrogen receptor-positive subtypes increased more than for women with estrogen receptor-negative subtypes.
Researchers concluded, "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. If verified, the increase is particularly concerning, because young age itself is an independent adverse prognostic factor for breast cancer, and the lowest 5-year breast cancer survival rates as a function of age have been reported for 20- to 34-year-old women. The most recent national 5-year survival for distant disease for 25- to 39-year-old women is only 31 percent according to SEER data, compared with a 5-year survival rate of 87 percent for women with locoregional breast cancer."