The number of women with late-stage, invasive breast cancer at the time of diagnosis increased significantly among U.S. women across all ages and ethnicities between 2004 and 2021, researchers reported in Radiology.

During that period, diagnoses of new breast cancer cases in which the disease had already spread in the body increased by an average of 1.16% per year, according to the report.

The biggest annual percentage increase in the incidence of metastatic breast cancer at diagnosis was 2.9%, seen in women between the ages of 20 and 39.

Among women aged 40–74 years, annual percentage increases were 2.1% from 2004 to 2012 and 2.7% from 2018–2021.

“It’s been previously reported that metastatic breast cancer at initial presentation has increased significantly for women under 40, but until now, no clear trend in older women has been reported,” study co-author Debra Monticciolo, MD, of the Foundation for Imaging Research and Education in Temple, Texas, said in a statement.

For women aged 75 years and older, the incidence rate increased by 1.4% over the study period.

The findings are drawn from the Surveillance, Epidemiology, and End Results database, which collected data on more than 71 million women each year.

Across ethnicities, Native American women had the largest annual percentage increase in rates of metastatic breast cancer at diagnosis, at 3.9%. The incidence in Asian women increased by 2.9% per year. Annual percentage changes among Black and Hispanic women were 0.86% and 1.6%, respectively.

Among white women, there was an annual percentage increase of 1.7% from 2004–2012, but no trend after that.

Incidence rates of metastatic breast cancers were 55% higher in Black women compared to white women, the researchers also reported.

“Fewer than 50% of U.S. women participate in annual breast cancer screening,” said Monticciolo, a past president of the American College of Radiology.

“That means we don’t have the opportunity to sweep out early-stage breast cancers in huge numbers of women, who will arrive at a later stage for diagnosis.”