Incidence rates of digestive cancers among U.S. military servicemen: Comparison with the rates in the general U.S. population

BACKGROUND: Digestive cancers greatly contribute to the cancer burden in the United States. These cancers are more common among men and some are increasing among adults under age 50. Military population, which is dominantly male and young, and general populations differ in exposure to risk factors for these cancers. However, no studies have systematically investigated whether the incidence rates of these cancers differ between the two populations. This study aimed to compare incidence rates and trends of select digestive cancers between active-duty military and general populations in men aged 20–59 years. METHODS: Data were from the Department of Defenses’ Automated Central Tumor Registry (ACTUR) and the National Cancer Institute’s Surveillance, Epidemiology, and End Results 9 (SEER-9) registries. Age-adjusted incidence rates of colorectal, stomach, liver, and pancreatic cancers among men aged 20–59 years during 1990–2013 were compared between the two populations. Stratified analyses by age were done for colorectal and stomach cancers. The joinpoint regression analysis was conducted to examine temporal trends for colorectal cancer. RESULTS: The age-adjusted incidence rates of colorectal, stomach, liver, and pancreatic cancers were overall lower among active-duty than SEER (IRR = 0.86, 95% CI = 0.81–0.92; IRR = 0.65, 95% CI = 0.55–0.76; IRR = 0.39, 95% CI = 0.30–0.49; IRR = 0.51, 95% CI = 0.41–0.62, respectively). This was observed in the groups of both ages 20–39 and 40–59 years for stomach cancer, and in the group of ages 40–59 years for colorectal cancer. The incidence rates of colorectal cancer tended to decrease since 2008 in ACTUR. CONCLUSION: The incidence rates for selected digestive cancers overall were lower in the active-duty military population than the U.S. general population. This study highlights the need for more research enhancing our understanding of variations in these cancers between the two populations.