Photo by Graham Colm
Researchers studying stored blood samples from Vietnam War veterans found that exposure to the herbicide Agent Orange was associated with a more than 2-fold increased risk of monoclonal gammopathy of undetermined significance (MGUS).
The team studied samples from US Air Force personnel who conducted aerial herbicide spray missions of Agent Orange during the war and compared them to blood samples from other Air Force vets.
The incidence of MGUS among the vets exposed to Agent Orange was low, at about 7%. But they still had twice the rate of MGUS as the other vets.
The researchers said this finding supports the previously discovered link between pesticides and myelomagenesis.
While the cause of MGUS and multiple myeloma (MM) remains largely unclear, studies have reported an elevated risk of MM among farmers and other agricultural workers. And pesticides have been thought to be the basis for these associations.
To further investigate the link, Ola Landgren, MD, PhD, of Memorial Sloan Kettering Cancer Center in New York, New York, and his colleagues conducted their study of Vietnam vets. The team reported the results in JAMA Oncology.
The researchers studied store blood samples from 958 male vets—479 Operation Ranch Hand vets who were involved in aerial herbicide spray missions and 479 Air Force vets who had similar duties in Southeast Asia during the same time period (1962 to 1971) but were not involved in herbicide spray missions.
The overall prevalence of MGUS was 7.1% in the Operation Ranch Hand vets and 3.1% in the comparison vets, which translates to a 2.4-fold increased risk for MGUS in Operation Ranch Hand vets.
The odds ratio—after the researchers adjusted for confounding factors such as race, age, and body mass index—was 2.37 (P=0.007).
Dr Landgren and his colleagues conceded that this study has limitations, including a lack of women and the potential for unknown confounding factors such as family medical history and civilian occupation.
Still, the researchers said their findings support an association between Agent Orange exposure and myelomagenesis.
In a related editorial, Niklhil C. Munshi, MD, of the Dana-Farber Cancer Institute in Boston, Massachusetts, said this study has implications beyond MGUS and MM.
“It also highlights the importance of tissue banking that allows investigation of a number of unanswered questions using modern methods,” Dr Munshi wrote. “The emphasis now is to store samples from almost every major study with correlative science in mind, and this is essential if we are to understand disease biology, mechanism of response, and resistance to therapy in the era of targeted therapy and precision medicine.”
