Incidence of brain metastases within the VA Healthcare System.

Abstract

e14691 Background: Advancements in cancer detection and treatment are thought to underlie decreasing cancer mortality rates. The influence of these on the development of brain metastases, which can be a driving factor for mortality, has not been addressed in a modern cohort. Methods: The age adjusted incidence (AAI) of brain metastases (BMs) from any primary and those with an underlying breast, colorectal, lung, kidney, or melanoma primary were calculated by federal fiscal year from 2005 through 2019 in the VA Healthcare System (VAHS) based on the timing of the first documentation of ICD9 or ICD10 codes in the patient’s medical record, The AAI rates were calculated based on the age distribution in VAHS and US census in 2020. Incidence proportions (IPs) were calculated by dividing the number of brain metastases with an underlying primary by the number of cases of that primary from 2005-2009. Results: 36,598 new BM cases of any underlying primary were diagnosed from 2005-2019. 96.2% of diagnoses were in men, 17.9% in African-Americans. The median age at diagnosis was 66.4 years old. 67.9% of BMs cases had a prior lung cancer diagnosis. The IP of lung, colorectal, kidney, melanoma, and breast cancer were 13.7%, 1.87%, 3.67%, 4.31%, and 3.08%, respectively. Overall, the AAI of BMs in the VAHS increased from 22.5 in 2005 to 24.6 in 2012 then decreased to 16.8 in 2019. Similar trends in the AAI of BMs with a lung, colorectal, kidney, or melanoma primary were observed (Table). The AAI of BMs with a breast primary increased from 2005 to 2019 (Table 1). The decrease in BM AAI from 2005 to 2019 paralleled decreases in lung (104.6 to 73.4), colorectal (63.9 to 37.5), kidney (27.5 to 26.4) and breast (140.5 to 136.1) cancer AAI as well as melanoma (28.2 to 21.7) AAI over the same time, respectively. Conclusions: In a modern cohort from the largest integrated health care system in the United States, the IPs of BMs from five primary sites associated with BMs were lower compared to older cohorts and the AAI rates decreased over time. Future studies will assess the impact of modern screening and treatment on BM incidence. [Table: see text]