Vietnam War veterans exposed to Agent Orange have a twofold higher prevalence of monoclonal gammopathy of undetermined significance (MGUS), compared with control veterans, providing the first scientific evidence for a link between the multiple myeloma precursor and Agent Orange exposure, researchers reported online in JAMA Oncology.
Serum samples from U.S. Air Force personnel who conducted aerial herbicide spray missions of Agent Orange in the Vietnam War from 1962 to 1971 (Operation Ranch Hand) were compared with samples from veterans who served in Vietnam during the same time period but were not involved in herbicide spray missions. The human carcinogen TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) was a contaminant found in variable amounts in Agent Orange, and levels of TCDD measured in the veteran’s serum samples were associated with cohort status. For example, TCDD levels greater than 10.92 parts per trillion were observed in 47.5% of the Ranch Hand cohort, compared with just 2.5% of the control veteran cohort. The risk of MGUS increased with increasing body burden of TCDD, although the trend was not significant.
MGUS prevalence in the Ranch Hand group was 7.1% (34 of 479) compared with 3.1% (15 of 479) in the control group (adjusted odds ratio, 2.37; 95% confidence interval, 1.27-4.44; P = .007).
“Our findings of increased MGUS risk among Ranch Hand veterans supports an association between Agent Orange exposure and multiple myeloma,” wrote Dr. Ola Landgren, Chief of Myeloma Service at Memorial Sloan Kettering, New York, and his colleagues (JAMA Oncol. 2015 Sep 3; [doi:10.1001/jamaoncol.2015.2938].
Serum samples were collected in 2002 from U.S. Air Force personnel who conducted aerial herbicide spray missions from 1962 to 1971 (n = 479) and control veterans who were not involved in the aerial missions (n = 479). The study was a follow-up of the Air Force Health Study. The first TCDD measurements were made in 1987, up to 25 years after Agent Orange exposure.
Ranch Hand veterans younger than 70 years had a significantly increased MGUS risk (OR, 3.4; 95% CI, 1.46-8.13; P = .004), but those older than 70 years had no increased MGUS risk.
Previous studies have pointed to an elevated risk of multiple myeloma among agricultural workers, and pesticides are thought to be responsible for the association.
The study was supported by the Agency for Toxic Substances and Disease Registry, the National Cancer Institute, and the Air Force Health Study Assets Research Program. Dr. Landgren reported having consulting or advisory roles with Onyx Pharmaceuticals/AMGEN, Celgene, Bristol-Myers Squibb, Jansen, and Millennium Pharmaceuticals/Takeda.