In 2014, one year after the formation of the MBC Alliance, we published Changing the Landscape for People Living with Metastatic Breast Cancer. Chapter 5 of the analysis showed a lack of data about the population of metastatic breast cancer (MBC) patients living across the US. We identified key questions to be answered about MBC epidemiology in the areas of incidence, prevalence, and outcomes survival.
The newly published study by Malmgren et al. is the third in a series of articles published on aspects of this topic.
The first article focused on the population across the US and estimated the number of people living with MBC. This study was done in partnership with the NCI SEER database statistical experts. The study authors found that about 155,000 people in the US are living with MBC.
The second article investigated key MBC epidemiology questions in more detail. The MBC Alliance and collaborators needed to work with a hospital that had a longitudinal database with a large number of cases with long-term follow-up. The key questions were about the incidence as well as outcomes in survival for recurrent MBC (rMBC) compared to de novo MBC (dnMBC). The SEER database is not suitable for such a study because it only captures dnMBC and not rMBC. The Swedish Cancer Institute in Seattle, Washington has a long-term cohort they have followed from 1990 through the present day. This study found that women with dnMBC had a 5-year survival rate of 44% compared to 20% of women with rMBC. Over the 20-year period, dnMBC 5-year survival improved by 27%, from 28% to 55%, but rMBC survival decreased over time.
The newly published study is the third in the series on MBC epidemiology. This study also investigated data from the Swedish Cancer Institute in Seattle. They studied over 8,000 women with stage I-III invasive breast cancer, 11.6% of whom were later diagnosed with rMBC. The authors found a significant decline in rMBC over time, but no increase in distant disease survival. They also looked at receptor subtypes in detail. The incidence of HER2+ and HR+ rMBC both decreased, but the incidence of triple negative (HER2− and HR−) rMBC did not, creating a relative increase in triple negative rMBC overall.
The MBC Alliance and collaborators are continuing their efforts to understand the epidemiology of MBC. Data from previous and future efforts will allow the MBC Alliance to develop policy messaging to better advocate for people living with MBC.
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