Traumatic brain injury, brain cancer linked in post 9/11 US military veterans

Key takeaways:

• Researchers examined data from more than 1 million post 9/11 US veterans.
• Despite the low incidence of brain cancer, outcomes were poor for those with moderate/severe and penetrating TBI.

In a cohort of post-9/11 United States military veterans, moderate, severe and penetrating traumatic brain injuries were associated with the subsequent development of brain cancer, according to research from JAMA Network Open.

“Very little is known about the association between exposures and subsequent brain cancer risk,” Ian J. Stewart, MD, director of the division of nephrology in the department of medicine at Uniformed Services University of Health Sciences in Maryland, and colleagues wrote. “One proposed exposure that might increase the risk of brain cancers is traumatic brain injury.”

Through a retrospective cohort study conducted from October 2004 to September 2019, Stewart and colleagues sought to examine whether a history of exposure to traumatic brain injury in U.S. military veterans who served after Sept. 11, 2001, carries any associations with subsequent development of brain cancer.

The researchers examined Veterans Affairs and Department of Defense administrative data of 1,919,740 veterans (median age 31 years; 80.25% male; 63.11% white) from the Long-Term Impact of Military-Relevant Brain Injury Consortium–Chronic Effects of Neurotrauma Consortium.

Documented TBI injuries were categorized as either mild, moderate or severe and penetrating, with the primary outcome development of brain cancer based on ICD-9 or ICD-10 diagnostic codes in either DoD/VA medical records or from the National Death Index.

The final cohort featured 449,880 individuals with TBI (mild, n = 385,848; moderate/severe, n = 46,859; penetrating, n = 17,173).

Data showed that brain cancer occurred in 318 individuals without TBI (0.02%), 80 with mild TBI (0.02%), 17 with moderate/severe TBI (0.04%), and 10 or fewer with penetrating TBI (0.06%).

After adjustment, moderate/severe TBI (adjusted HR = 1.9; 95% CI: 1.16-3.12) and penetrating TBI (aHR = 3.33; 95% CI: 1.71-6.49), but not mild TBI (aHR = 1.14; 95% CI: 0.88-1.47) were associated with the subsequent development of brain cancer.

“While the absolute number of brain cancer diagnoses was small, these diagnoses are associated with profoundly poor outcomes,” Stewart and colleagues wrote.

In a related editorial, Elie Massaad, MD, a research fellow in the department of neurosurgery at Massachusetts General Hospital, praised Stewart and colleagues for bringing to light associations between trauma suffered in combat and long-term health outcomes. “This study provides meaningful data clarifying associations between combat-related TBI severity and subsequent brain cancer risk,” he wrote.

Reference:

Massaad E, et al. JAMA Netw Open. 2024;doi:10.1001/jamanetworkopen.2023.54546.