The incidence of breast cancer presenting with distant involvement has risen significantly over the past 30 years among young women, and this trend shows no signs of abating, according to a report in the Feb. 27 issue of JAMA. In contrast, the rate of locoregional breast cancer has not increased in this age group, and the incidence of all stages of the disease have not shown any increasing trends among older women, said Dr. Rebecca H. Johnson of Seattle Children's Hospital and the University of Washington, Seattle, and her associates.
This trajectory "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" lost, the investigators noted.
They used data from three of the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) registries to examine time trends in breast cancer between 1976 and 2009. They found a steady, and possibly accelerating, rise in the rate of women aged 25-39 years presenting with metastatic breast cancer, from 1.53/100,000 in 1976 to 2.90/100,000 in 2009.
"No other age group had statistically significant increases, either for distant, regional, or localized disease at diagnosis," Dr. Johnson and her colleagues said (JAMA 2013;309:800-5).
In a different analysis of the data, the category of metastatic breast cancer as a proportion of all invasive breast cancer in this age group rose from 4.4% in the 1970s to 4.8% in the 1980s, 5.5% in the 1990s, and 7.2% in the early 2000s.
This trend was evident in women of all races/ethnicities, in women residing in both urban and nonurban regions, and in women with estrogen receptor-positive and estrogen receptor-negative tumors. "Non-Hispanic white and African-American individuals appear to have been more affected by the increase, as have women with the ER-positive subtype of the disease," they said.
"The absolute increase of 1.37/100,000 over 34 years is relatively small, but the trend shows no evidence of abatement and may indicate increasing epidemiologic and clinical significance," the researchers said.
These findings must be corroborated in other studies. If they are confirmed, they will be particularly concerning "because young age itself is an independent adverse prognostic factor for breast cancer.
"The most recent national 5-year survival data for distant disease for 25- to 39-year-old women is only 31% ... compared with a 5-year survival of 87% for women with locoregional breast cancer," they added.