Military cancer outcomes research (MilCan): A sub-study of the Millennium Cohort Study

Background: Cancer remains a leading cause of death in the US, and US service members and veterans have higher rates of certain cancers than the US general population. Military-specific occupational exposures, such as aviation-related ultraviolet radiation exposure, chemical toxicants, and blasts leading to immune system dysregulation have been hypothesized to have long-term implications for cancer risk. Methods: The Millennium Cohort Study (MCS) is a large-scale, prospective cohort study designed to examine the long-term health effects of military service. Over 260,000 US service members were enrolled between 2001 and 2021, and follow-up of participants is planned through 2068. As the cohort matures, there is increased focus on age-related diseases such as cancer. The MCS has collected longitudinal survey data on well-established cancer risk and protective factors, such as tobacco and alcohol use, physical activity, and obesity. The Military Cancer Outcomes Research (MilCan) initiative aims to develop a military cancer data warehouse platform that will link data from various military and civilian data sources (eg, electronic health records, military environmental exposures, lifestyle behaviors, and tumor biology, pathology, and imaging). Results: Preliminary analyses of available survey and medical record data suggest there are at least 11,000 occurrences of cancer in the MCS. The study team is in various stages of linking with the (1) Department of Defense Cancer Registry, a centralized database of patients diagnosed with cancer in the Military Health System; (2) Virtual Pooled Registry Cancer Linkage System, a web-based, streamlined process for researchers to conduct minimal risk linkage studies with the nationwide resource of Central Cancer Registries; (3) Joint Pathology Center, which is part of the Defense Health Agency and maintains the world's largest collection of human pathology specimens; and (4) Individual Longitudinal Exposure Record, which includes historical deployment information and occupational exposures. Conclusion: The planned data and specimen linkages with MCS survey data will allow MilCan to conduct population-based research on a wide range of military occupational, environmental, and behavioral exposures on the etiology of cancer among post-9/11 service members and veterans and could inform the development of policies and programs to prevent cancer.