Breast cancer and serum organochlorines: a prospective study among white, black, and Asian women.
BACKGROUND
Five small case-control studies have examined the relationship between exposure to organochlorines and the risk of breast cancer and have found inconsistent results. In these studies, organochlorine levels in breast cancer patients were measured after (or at most 6 months before) diagnosis.


OBJECTIVE
We tested the hypothesis that organochlorines are a risk factor for breast cancer, using prospectively gathered data on serum levels of DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] (the main metabolite of the pesticide DDT [2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane]) and polychlorinated biphenyls (PCBs).


METHODS
Study subjects belonged to a cohort of 57,040 women (46,629 white, 8123 black, and 2288 Asian) from the San Francisco Bay Area who took a multiphasic health examination, independent of concern about risk of breast cancer, in the late 1960s. At that time, a sample of blood was obtained, then frozen and stored. Follow-up was through December 31, 1990. We conducted a nested case-control study of 150 case patients and 150 matched control subjects. A random sample of 50 women per racial/ethnic group who had been diagnosed with breast cancer more than 6 months after the multiphasic examination (mean follow-up = 14.2 years) was selected, and each case patient was matched to a cancer-free control subject.


RESULTS
Matched analyses found no differences in the case patients' and control subjects' serum levels of DDE (mean difference = 0.2 parts per billion [ppb]; 95% confidence interval [CI] = -6.7, 7.2) or PCBs (mean difference = -0.4 ppb; 95% CI = -0.8, 0.1). DDE levels, however, tended to be higher among black case patients compared with black controls (mean difference = 5.7 ppb; 95% CI = -3.3, 14.8), and PCBs were lower among white case patients compared with white controls (mean difference = -0.6 ppb; 95% CI = -1.2, -0.1). Organochlorine levels were significantly higher among black and Asian women compared with white women. The mean difference for DDE was 11.0 ppb for black women (95% CI = 4.3, 17.6) and 12.6 ppb for Asian women (95% CI = 6.0, 19.2); for PCBs, the respective differences were 0.8 ppb for black women (95% CI = 0.2, 1.4) and 1.4 ppb for Asian women (95% CI = 0.8, 1.9). The results were not altered by adjusting for relevant confounders, and the lack of association between exposure to organochlorines and breast cancer was present regardless of length of follow-up, year of diagnosis, or the case patient's menopausal and estrogen-receptor status.


CONCLUSIONS
The data do not support the hypothesis that exposure to DDE and PCBs increases risk of breast cancer.


CONCLUSIONS
Future investigations must consider the biologic mechanisms involved and variations in exposure to chemical pollutants and of breast cancer incidence rates among diverse groups of women.
Krieger
N
N
Division of Research, Kaiser Foundation Research Institute, Oakland, Calif. 94611.
Wolff
M S
MS
Hiatt
R A
RA
Rivera
M
M
Vogelman
J
J
Orentreich
N
N
D000328:Adult; D044466:Asian People; D044383:Black People; D001943:Breast Neoplasms / Q000097:blood* / Q000139:chemically induced / Q000208:ethnology; D016022:Case-Control Studies; D003633:Dichlorodiphenyl Dichloroethylene / Q000097:blood; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D006801:Humans; D007306:Insecticides / Q000097:blood*; D008875:Middle Aged; D015999:Multivariate Analysis; D011078:Polychlorinated Biphenyls / Q000097:blood; D011446:Prospective Studies; D012307:Risk Factors; D044465:White People
D007306:Insecticides; D003633:Dichlorodiphenyl Dichloroethylene; D011078:Polychlorinated Biphenyls