Occupational exposure to P,P'-dichlorodiphenyl-trichloroethane (DDT) has be
en associated with increased pancreatic cancer risk. We measured organochlo
rine levels in serum obtained at the study enrollment from 108 pancreatic c
ancer cases and 82 control subjects aged 32- 85 years in the San Francisco
Bay Area between 1996 and 1998. Cases were identified using rapid case-asce
rtainment methods; controls were frequency-matched to cases on age and sex
via random digit dial and random sampling of Health Care Financing Administ
ration lists. Serum organochlorine levels were adjusted for lipid content t
o account for variation in the lipid concentration in serum between subject
s. Median concentrations of p,p'-dichloradiphenyldichloroethylene (DDE, 129
0 versus 1030 ng/g lipid; P = 0.05), polychlorinated biphenyls (PCBs; 330 v
ersus 220 ng/g lipid; P < 0.001), and trans-nonachlor (54 versus 28 ng/g li
pid; P = 0.03) were significantly greater among cases than controls. A sign
ificant dose-response relationship was observed for total PCBs (P for trend
< 0.001), Subjects in the highest tertile of PCBs (greater than or equal t
o 360 ng/g lipid) had an odds ratio (OR) of 4.2 [95% confidence interval (C
I) = 1.8-9.4] compared to the lowest tertile, The OR of 2.1 for the highest
level of p,p'-DDE (95% CI = 0.9-4.7) diminished (OR = 1.1; 95% CI = 0.4-2.
8) when PCBs were included in the model. Because pancreatic cancer is chara
cterized by cachexia, the impact of this on the serum organochlorine levels
in cases is difficult to predict. One plausible effect of cachexia is bioc
oncentration of organochlorines in the diminished lipid pool, which would l
ead to a bias away from the null. To explore this, a sensitivity analysis w
as performed assuming a 10-40% bioconcentration of organochlorines in case
samples. The OR associated with PCBs remained elevated under conditions of
up to 25% bioconcentration.