some point during their lifetime. Cancer can develop at any age, but about 77% of all cancers are diagnosed in people 55 of age and older. Military personnel during the Gulf War were had a mean age of 28 years, thus it is likely too early for the development of most cancers in Gulf War veterans. Cancer strikes Americans of all racial and ethnic groups, and the rate at which new cancers occur (the incidence) varies from group to group (ACS 2006).

The mortality and hospitalization studies reviewed later in this chapter do not definitively identify overall increases in cancer among Gulf War veterans. However, there are other studies that have examined the possibility of brain and testicular cancer. Those cancer studies are evaluated in this section. Because few of the studies dealt with specific cancers, this section groups primary and secondary studies together.

Primary and Secondary Studies

Brain Cancer

Brain cancer is relatively rare. The annual age-adjusted incidence of brain cancer in the United States is 6.4 cases per 100,000 men and women. The median age at diagnosis of brain cancer is 55 years; about 22% of cases are diagnosed between the ages of 20-44 years old (Ries et al. 2005). There is one published study of brain cancer in Gulf War veterans.

Bullman and colleagues assessed cause-specific mortality among the 100,487 Gulf War veterans identified with the 2000 sarin plume model (described in Chapter 2) as having been subjected to nerve-agent exposure from the March 1991 demolition of weapons at Khamisiyah (Bullman et al. 2005). Compared with 224,980 Gulf War veterans similarly deployed but considered unexposed to the plume, there was an increased risk of brain cancer deaths with followup through December 31, 2000 (relative risk [RR] 1.94, 95% confidence interval [CI] 1.12-3.34). There was also a suggestion of a dose-response relationship, with the risk increasing from those who were unexposed to those exposed for 1 day to those exposed for 2 days. Specific subtypes of brain cancer were not considered. Because brain cancer is considered to have a latent period of 10-20 years, and the study included less than 9 years of followup, the results should be interpreted with caution. Further followup is necessary to draw any conclusions about the risk of brain cancer among Gulf War veterans.

Testicular Cancer

Two articles have focused specifically on testicular cancer. Testicular cancer is relatively uncommon in the United States. The annual age-adjusted incidence is 5.3 cases per 100,000 men. However, it is one of the few cancers whose usual age of onset is in the same range as the age of the Gulf War veterans, about 20 to 44 years old (Ries et al. 2005). In general, little is known about environmental risk factors for testicular cancer.

Knoke and colleagues (1998) examined testicular cancer among US servicemen on active duty during the time of the Gulf War (August 8, 1990, through July 31, 1991) and who remained on active duty at the end of the deployment period. Eligible servicemen included 517,223 people deployed to the gulf and 1,291,323 nondeployed. The authors identified cases of all first-hospital admissions, in US military hospitals worldwide, for a principal diagnosis of testicular cancer from the period of July 31, 1991 through April 1, 1996. Cases were identified by examining the DOD hospitalization database through April 1, 1997. A total of 505 cases were ascertained: 134 among the deployed and 371 among the nondeployed. In Cox proportional-hazards models adjusted for race and ethnicity, age, and occupation, no association with deployment status was

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