In the United States, the incidence of advanced breast cancer among women aged 25 to 39 has increased over the past thirty years, finds study.
Published in the Journal of the American Medical Association, the study found that cases increased from 1.53 per 100,000 in 1976 to 2.90 per 100,000 in 2009.
According to the researchers, that represents an average compounded increase of 2.07 percent per year over the 34-year period.
While that is a relatively small increase, "the trend shows no evidence for abatement and may indicate increasing epidemiologic and clinical significance," wrote the authors of the study headed by Rebecca Johnson of the Seattle Children's Hospital and the University of Washington.
The statistics used for the study came from three US National Cancer Institute Surveillance, Epidemiology and End Results registries.
"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," according to the authors.
The researchers found that the greatest uptick occurred among 25 to 34-year-olds, with progressively smaller increases occurring in older women, as measured in five-year intervals. There was no statistically significant incidence rise in women over the age of 55, they wrote.
For women aged 25 to 39, the increases were "statistically significant" in African American and non-Hispanic whites since 1992, when race and ethnicity became available in the data used.
"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.