Epidemiological trends, prognostic factors, and survival outcomes of synchronous brain metastases from 2015 to 2019: A population-based study

Background: Brain metastases (BM) constitute a significant cause of oncological mortality. Statistics on the incidence of BM are limited because of the lack of systematic nationwide reporting. We report the incidence of synchronous brain metastases (sBM), defined as BM identified at the time of primary cancer diagnosis from 2015 to 2019 using National Cancer Institute's (NCI's) Surveillance, Epidemiology, and End Results Program database. Methods: We identified 1,872,057 patients with malignancies diagnosed between 2015 and 2019 from the SEER 17 Registries database, including 35,986 (1.9%) patients with sBM. Age-adjusted incidence rates were examined using the NCI Joinpoint software. Kaplan-Meier curves and a multivariate Cox regression model were used to investigate survival. Results: The incidence rate of sBM from 2015 to 2019 was 7.1 persons per 100,000. Lung and bronchus cancers had the highest incidence of sBM (5.18 to 5.64 per 100,000), followed by melanoma (0.30 to 0.34 per 100,000) and breast cancers (0.24 to 0.30 per 100,000). In children, renal tumors had the highest sBM incidence. sBM were associated with poorer survival than extracranial metastases only (hazard ratio [HR]: 1.40 [95% CI: 1.39-1.42], P <. 001). We observed better survival in white patients relative to nonwhite patients with sBM (HR: 0.91 [95% CI: 0.90-0.94], P <. 001). Conclusions: The incidence rate of sBM has remained similar to rates reported over the last 9 years, with the majority associated with primary lung and bronchus cancers. sBM represent a national healthcare burden with tremendous mortality in pediatric and adult populations. This population may benefit from improved screening and treatment strategies.