SEATTLE The likelihood that a woman in the age range of 25 to 39 will be diagnosed with advanced breast cancer has steadily increased since the mid-1970s, researchers from Seattle Children’s and Oregon Health and Science University have found.
Analyzing data from hundreds of thousands of cases collected in three national cancer registries, the researchers, whose work is published in Wednesday’s issue of Journal of the American Medical Association, found no other age group had such an increase.
Although breast cancer overall is relatively rare in younger women, it is the most common malignant tumor in young adult women, who tend to experience more aggressive disease and have lower survival rates, the study’s authors said.
The study looked at the extent of the disease at the time of original diagnosis, comparing the change in incidence in each age group from 1976 to 2009.
The increase in incidence of metastatic disease in the 25-39 age group was small – an increase of 1.37 cases per year for every 100,000 women – but statistically significant and steady throughout the time period, said the study’s lead researcher, Dr. Rebecca Johnson, medical director of the Adolescent and Young Adult oncology program at Seattle Children’s.
Since 1992, when data on race and geographic location were added to the databases, the increase among women in that age group occurred in all races and ethnicities evaluated and in both metropolitan and nonmetropolitan areas, the researchers said.
Non-Hispanic white women and African-American women, as well as women with estrogen-receptor positive subtypes of cancer, appear to have been most affected.
Over the time period analyzed in the study, the number of women ages 25-39 in the U.S. grew from about 22 million to approximately 28 to 30 million – a figure that’s been steady since the 1980s, Johnson noted. That’s an increase of about 36 percent.
But in the same period, the number of women in that age group with an original diagnosis of metastatic breast cancer increased from 293 in 1976 to 838 in 2009, an increase of 186 percent.
No other age group had a similar increase.