Prostate cancer in US Air Force veterans of the Vietnam war

US Air Force veterans of Operation Ranch Hand sprayed herbicides contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin ( TCDD) in Vietnam from 1962 to 1971. Comparisons served in Southeast Asia ( SEA) during the same time period but did not spray herbicides. Here we investigate a potential association between exposure to TCDD and prostate cancer. Data were available for 2516 veterans ( 1019 Ranch Hand and 1497 Comparison) who participated in at least one of six physical examinations starting in 1982 and had a measurement of serum TCDD. We assigned Ranch Hands to two exposure categories: Lower and Higher, based on their median 20-year cumulative TCDD level. In total, 81 Comparison and 59 Ranch Hand prostate cancers were identified between 1 January 1982 and 31 December 2003. We found no overall increase in the risk of prostate cancer in Ranch Hand veterans versus the Comparisons. There was a positive association in Ranch Hand veterans in the Higher TCDD category who served in SEA before 1969 (RR = 2.27, 95% CI 1.11-4.66) when more contaminated herbicides were used, but the number of cases was small (n = 15). A within- group comparison found that in Comparison veterans, time served in SEA was associated with an increased risk of prostate cancer ( RR = 2.18, 95% CI 1.27 - 3.76, 4789 days versusr <= 789 days). No increase in the risk of prostate cancer was observed within the Ranch Hand group in association with TCDD or time served in SEA. These analyses suggest that a longer service in SEA and exposures other than TCDD may have increased the risk of prostate cancer in Comparison veterans.