Middle East Deployment and Lymphoid Malignancies in US Veterans: A Matched Case-Control Analysis

<b>Background/Objective:</b> US military personnel deployed to the Middle East were potentially subjected to harmful exposures, such as carcinogens from burn pits, which may increase the risk of lymphoid malignancies. Our objective was to determine the association between deployment and the risk of developing lymphoid malignancies. <b>Methods:</b> This was a retrospective nested matched case-control study from a cohort of 3.5 million veterans who enlisted in the military after September 2001 and were followed until death or last follow up through September 2024. Cases of lymphoid malignancies were identified by the VA Central Cancer Registry and controls were randomly selected from the same base cohort, matched by year of birth, year of enlistment, sex, race, and ethnicity. Exposure was defined as deployment to the Middle East as determined by identification on the VA Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF) roster with confirmed dates of deployment or paystubs. <b>Results:</b> There were 1037 cases of lymphoid malignancies and 3572 matched controls. Deployment was not associated with a higher risk of developing lymphoid malignancies compared to non-deployment. Exposure to OEF/OIF was not associated with a higher risk of developing certain types of lymphoid malignancies. <b>Conclusions:</b> In this large, matched case-control study of US veterans, deployment to the Middle East was not associated with increased risk of developing lymphoid malignancies. While these findings do not support an increased lymphoid malignancy risk, important limitations remain, including the absence of detailed exposure and potential confounding variables. Prospective monitoring of specific types and doses of exposures during military deployment, development of lymphoid and other malignancies, and their underlying pathophysiology is indicated.