Environment and Breast Cancer: Science Review

Evidence From Humans
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Plasma organochlorine levels and the risk of breast cancer: an extended follow-up in the Nurses' Health Study
Laden, F., Hankinson, S. E., Wolff, M. S., Colditz, G. A., Willett, W. C., Speizer, F. E., Hunter, D. J. International Journal of Cancer. 2001. 91:4, 568-74.
Topic area
Environmental pollutant - Pesticides, organochlorines
Study design
Nested case-control
Funding agency
Other: US NIM
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Post menopausal
Number of Controls
Controls: 381
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Women in the Nurses' Health Study who were registered nurses between 30 and 55 years old at enrollment in 1976 and resident in 11 large states. Cases did not have breast cancer at the time of blood draw and were diagnosed before June 1994. Limited to postmenopausal diagnoses. Controls matched on birth year, menopausal status, post-menopausal hormone use, blood collection date/time, fasting status at blood draw.
Exposure Investigated
Exposures investigated
p,p'-DDE, 21 PCB congeners, sum of 16 higher congeners. Blood sample drawn in 1989-90. Lipid-adjusted concentration in plasma, divided in quintiles.
Exposure assessment comment
Exposure measure may or may not correctly rank the exposures relevant to disease. Exposure measure is 10 years after the chemicals were banned and is subject to effects of time since exposure, parity and lactation, recent diet, weight loss. Consideration of selected organochlorines independent of other chemicals in this class may be problematic.
Statistical Analysis
Breast cancer outcome investigated
Primary breast cancer: ER+, ER-, progesterone receptor positive
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
Age at menopause, age at menarche, parity, age at first full-term pregnancy, body mass index at blood collection, history of benign breast disease, history of breast cancer in a mother or sister.
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
Conditional logistic regression, test for trend, tests for interaction
Strength of associations reported
No statistically significant effect on risk. No interaction with body mass, lactation. Concentrations of p,p'-DDE and PCBs were generally lower in cases than controls.
Nulliparous women with the highest PCB levels had higher risk (RR=5.30; 95% CI 1.06-26.57), but numbers were small (12 cases).
cases/controls; multivariate RR (95% CI)
quintile 2: 85/75; RR = 0.95 (0.59-1.53)
quintile 3: 48/74; RR = 0.51 (0.31-0.86)
quintile 4: 83/75; RR = 0.91 (0.57-1.47)
quintile 5: 68/74; RR = 0.82 (0.49-1.37)

quintile 2: 65/74; RR = 0.73 (0.44-1.21)
quintile 3: 65/74 RR = 0.75 (0.44-1.28)
quintile 4: 80/74; RR = 0.85 (0.49-1.47)
quintile 5: 74/74; RR = 0.84 (0.47-1.52)
Results Comments
Limitations in exposure measurement. If chemical exposures effect body mass or age at menarche or menopause, matching and controlling for these variables could obscure the relationship between exposure and disease.
Author address
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 181 Longwood Ave, Boston, MA 02115, USA. francine.laden@channing.harvard.edu