Estimation of the Number of Women Living with Metastatic Breast Cancer in the United States

We used a back-calculation method to estimate MBC prevalence from U.S. breast cancer mortality and survival from the Surveillance, Epidemiology and End Results (SEER) registries. On the basis of the illness–death process, this method assumes that each observed breast cancer death is the result of MBC, either de novo or a recurrence with metastatic disease.

We estimate that by January 1, 2017, there will be 154,794 women living with MBC in the United States, three in four initially diagnosed with stage I–III breast cancer who later progressed to MBC. Median survival and 5-year relative survival for de novo MBC increased over the years, especially in younger women. We estimate a two-fold increase in 5-year relative survival rate from 18% to 36%, for women diagnosed with de novo MBC at age 15–49 between 1992–1994 and 2005–2012, respectively.