Estimating the annual frequency of synchronous brain metastasis in the United States 2010-2013: a population-based study.

Brain metastases (BM) are one of the most common types of brain tumors and are a relatively common event in the disease process for several high-incidence cancer types, including breast and lung cancers. Historically, information on metastases including BM have not been collected as part of national cancer registration in the US, but BM at time of primary cancer diagnosis (SBM), is now collected by the National Cancer Institute's (NCI) Surveillance, Epidemiology, and End Results (SEER) system. Using data from 18 SEER registries from 2010 to 2013, we assessed the frequency of SBM at time of primary diagnosis in the US by site, histology group, sex, race, age, and insurance status. There were 1,634,954 total primary cancer cases in SEER from 2010 to 2013, 1.7% of which presented with SBM. The cancer type with the highest proportion of SBM was lung cancer (10.8% of cases with SBM), followed by esophageal (1.5%), kidney (1.4%), and melanoma (1.2%). SBM varied by age, sex, race, and insurance status for most histologies. Our results reflect the high proportion of patients who are diagnosed with lung cancer at late stages and present with SBM, in contrast to other common cancers in the US where SBM is less common. Demographic variation in molecular subtype and risk behavior may influence variation in SBM. BM is a relatively common event in late stage cancer and cause significant morbidity and mortality, and assessment of accurate population-based data is critical to estimate total disease burden.