Effect of Exposure to Agent Orange on the Risk of Monoclonal Gammopathy and Subsequent Transformation to Multiple Myeloma: A Single-Center Experience From the Veterans Affairs Hospital, Detroit

Abstract

Background: Monoclonal gammopathy of undetermined significance (MGUS) is an indolent, premalignant plasma cell disorder with the potential of transforming into symptomatic multiple myeloma (MM). There are multiple risk factors that contribute to transformation. Agent Orange (AO) has been linked with multiple malignant and nonmalignant conditions.

Patients and methods: We conducted a retrospective chart review of patients with monoclonal gammopathy who were seen at John D. Dingell Veterans Affairs Medical Center (Detroit, Michigan) between 2005 and 2015 with MGUS, smoldering multiple myeloma, and MM. We explored baseline patient characteristics and explored AO exposure. Dates of diagnosis, dates of progression, and expiration dates were recorded to time to progression and overall survival (OS).

Results: We identified 211 patients with monoclonal gammopathy; 96% were male and 122 were African American. Eleven patients had reported AO exposure. Cumulative risk of progression in the overall population was 1.4% at 1 year. Risk of transformation in the population exposed to AO was significantly higher with a hazard ratio (HR) of 11.19 (95% confidence interval [CI], 2.10-59.47; P = .005). OS was numerically shorter in AO-exposed patients with a median OS of 7 years compared with 11.1 years in those not exposed. However, AO exposure was not associated with OS in multivariable analysis (HR, 0.50; 95% CI, 0.07-3.83; P = .508).

Conclusion: Monoclonal gammopathy is a premalignant condition with the risk of progressing to MM. Exposure to AO has been implicated in multiple conditions including MM. Our study demonstrates an increased risk of progression in exposed patients.

Keywords: MGUS; Monoclonal gammopathy of unknown significance; Myeloma transformation; Pesticide; Progression to myeloma.