DICHLORODIPHENYLTRICHLOROETHANE SERUM LEVELS AND BREAST-CANCER RISK -A CASE-CONTROL STUDY FROM MEXICO

Some, but not all, epidemiological studies have suggested that dichlor odiphenyltrichloroethane (DDT) may play a role in the development of b reast cancer. These investigations have been conducted in countries wh ere this substance has been banned for at least 20 years. We conducted a study in Mexico, a country in which DDT is still being used to cont rol malaria. In a hospital-based case-control study, we compared 141 h istologically confirmed cases of breast cancer with 141 age-matched co ntrols (+/-3 years). All subjects were identified at three referral ho spitals of Mexico City between March 1994 and April 1996. Reproductive histories and other variables were obtained by structured interviews, DDT/DDE levels were determined in serum by gas-liquid chromatography. The arithmetic mean of serum DDE in lipid basis was 562.48 +/- 676.18 ppb (range, 10.24-4661.44) for the cases and 505.46 +/- 567.22 ppb (r ange, 0.004 to 4361.75) for the controls, but this difference was not statistically significant. The age-adjusted odds ratios for breast can cer regarding the serum level of DDE were 0.69 (95% confidence interva l, 0.38-1.24) and 0.97 (confidence interval, 0.55-1.70) for the contra sts between tertile 1 (lowest level) and tertiles 2 and 3, respectivel y. These estimates were unaffected by adjustment for body mass, accumu lated time of breastfeeding and menopause, and other breast cancer ris k factors. These results do not lend support to the hypothesis that DD T is causally related to breast cancer at the body-burden levels found in our study population but do not exclude the possibility that highe r levels of exposure could still play a role in the etiology of this t umor.