Agent orange as a risk factor for positive prostate biopsy.

Abstract

178 Background: Agent Orange (AO), a defoliate contaminated with the known carcinogen dioxin, has become a prominent concern as veterans of the Vietnam War who were exposed to AO are now reaching the age at which prostate cancer is most prevalent. While sufficient evidence has linked AO exposure to many diseases, only limited but suggestive evidence exists to support a positive association between AO and prostate cancer. Despite mixed findings, recent studies have found that the risk of prostate cancer in those exposed to AO was as high as twice the risk in those not exposed. The goal of this study was to examine this association between AO exposure and prostate cancer in a cohort of men referred for a prostate biopsy. Methods: In this retrospective cohort-design, risk factors were identified using historical clinical data from a population of veterans referred to the Portland VA Hospital for a prostate biopsy between 1993 and 2010. In addition to AO exposure, covariates included prostate specific antigen density (PSAD), results of the digital rectal exam (DRE), age at biopsy, family history, body mass index (BMI), race, and medication use. Outcomes of the biopsies were defined as either positive or negative according to the pathology report and risk factors were compared between individuals found to have prostate cancer and those without cancer. Multiple logistic regression was used to evaluate the effect of AO on risk of prostate cancer after adjustment for confounders. Results: Of the 2,720 veterans who underwent prostate biopsy, 896 (32.9%) were found to have prostate cancer. After adjustment for significant confounders including PSAD, DRE, age at biopsy, and family history of prostate cancer, veterans with prostate cancer were 49% more likely to have been exposed to AO as compared to those without prostate cancer (odds ratio = 1.49; 95% CI: 1.06-2.11, p=0.022). Conclusions: Agent Orange exposure was associated with a significant increase in prostate cancer detection in men referred for a prostate biopsy. The limitations in identifying biologically significant levels of AO exposure in this study may suggest potential for underestimation of the true risk. This study supports the findings of recent studies suggesting that AO exposure increases the risk of prostate cancer. No significant financial relationships to disclose.