Treatment for breast cancer and blood levels of chlorinated hydrocarbons.

Small studies have examined, with conflicting results, whether breast cancer risk is increased among women exposed to high levels of chlorinated hydrocarbons, as measured in breast fat tissue or peripheral blood collected prior to treatment (pretreatment blood). For a population-based, case-control study, collection of pretreatment blood is a labor-intensive effort. An alternative is to collect blood from cases at interview, as is done for controls, after breast cancer treatment has commenced (posttreatment blood). It is unknown whether treatment affects blood levels of the organochlorines 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) or polychlorinated biphenyls (PCBs). The purpose of this study was to determine whether pretreatment versus posttreatment blood samples yielded significantly different estimates of cumulative exposure to DDE and PCBs among newly diagnosed breast cancer patients. Two-ml blood samples were collected prior to and after treatment for breast cancer from 22 nonfasting women, ages 45-87 years, newly diagnosed with invasive disease. Treatment was defined as major surgery (mastectomy or node removal), radiation, hormones (tamoxifen), or chemotherapy. Pretreatment and posttreatment blood samples were assayed for DDE and PCBs in blinded, matched pairs. The reported concentrations (volume basis) were adjusted for estimated total plasma lipids. For DDE, mean differences in unadjusted [0.99 ng/ml; 95% confidence interval (CI), -0.36 to 2.34 ng/ml] and lipid-adjusted (0.05 microgram/g lipid; 95% CI, -0.04 to 0.13 microgram/g lipid) levels were small. For PCBs, the unadjusted (0.68 ng/ml; 95% CI, 0.05 to 1.30 ng/ml) and adjusted (0.070 microgram/g lipid; 95% CI, -0.009 to 0.149 microgram/g lipid) mean differences were of borderline statistical significance. The mean percent change in lipid-adjusted organochlorine levels did not vary substantially between treatment groups, except for those patients receiving chemotherapy [n = 5; 15.8% (DDE), 29.4% (PCBs)]. Adjusted mean differences also increased with increasing time between the pretreatment and posttreatment blood draws. In multiple regression models that included treatment, age, race, stage, and time between blood draws, only chemotherapy appeared to predict the percent change in adjusted pretreatment and posttreatment levels of DDE or PCBs (P = 0.10 and 0.06, respectively). Posttreatment blood samples drawn within 3 months of pretreatment samples, with the exception of those drawn after the commencement of chemotherapy, provide similar measures of DDE body burden levels among breast cancer cases. The use of blood samples collected after treatment, rather than before treatment, for characterizing PCB levels may lead to misclassification of exposure.