Study Estimates Number of U.S. Women Living with Metastatic Breast Cancer

A new study shows that the number of women in the United States living with distant metastatic breast cancer (MBC), the most severe form of the disease, is growing. This is likely due to the aging of the U.S. population and improvements in treatment. 

Researchers came to this finding by estimating the number of U.S. women living with MBC, or breast cancer that has spread to distant sites in the body, including women who were initially diagnosed with metastatic disease and those who developed MBC after an initial diagnosis at an earlier stage.

The researchers also found that median and 5-year relative survival for women initially diagnosed with MBC is improving, especially among younger women.

The findings appeared online on May 18 in Cancer Epidemiology, Biomarkers & Prevention.

In documenting the prevalence of MBC, the findings point to the need for more research into how to address the health care needs of women who live with this condition. 

“Even though this group of patients with MBC is increasing in size, our findings are favorable,” said Dr. Angela Mariotto, chief of NCI’s Data Analytics Branch. “This is because, over time, these women are living longer with MBC. Longer survival with MBC means increased needs for services and research. Our study helps to document this need.”

Although researchers have been able to estimate the number of women initially diagnosed with MBC, data on the number of women whose cancers spread to a distant organ site, either as a progression or a recurrence after being first diagnosed with an earlier stage of breast cancer, has been lacking because U.S. registries do not routinely collect or report data on recurrence. 

To develop a more accurate estimate of the total number of women living with MBC, researchers used data from NCI’s Surveillance, Epidemiology, and End Results Program to include women who developed MBC after diagnosis. The researchers estimated that, as of Jan. 1, 2017, more than 150,000 women in this country were living with MBC, and that 3 in 4 of them had initially been diagnosed with an earlier stage of breast cancer.

“These findings make clear that the majority of MBC patients, those who are diagnosed with non-metastatic cancer but progress to distant disease, have never been properly documented,” said Mariotto. “This study emphasizes the importance of collecting data on recurrence at the individual level in order to foster more research into the prevention of recurrence and the specific needs of this growing population.”