Environment and Breast Cancer: Science Review

Evidence From Humans
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Adipose levels of dioxins and risk of breast cancer
Reynolds, P., Hurley, S. E., Petreas, M., Goldberg, D. E., Smith, D., Gilliss, D., Mahoney, M. E., Jeffrey, S. S. Cancer Causes and Control. 2005. 16:5, 525-35.
Topic area
Environmental pollutant - Dioxin, PCDD, PCDF
Study design
Hospital based case-control
Funding agency
DOD Other: California Breast Cancer Research Progr
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number of Controls
Controls: 52
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Women undergoing breast biopsy at three San Francisco area hospitals during the mid 1990s. Women with atypical hyperplasia or carcinoma in situ were excluded. Women with previous (non-skin) cancer or previous radiation or Tamoxifen treatment were excluded.
Comment about participation selection
Controls with benign breast disease are not representative of the general population.
Exposure Investigated
Exposures investigated
Breast adipose from beyond edge of biopsy or excision cavity; or for women undergoing mastectomy, a site distant from the tumor. Analyzed for 17 dioxins and furans in picograms per gram lipid. Self reported diet
Exposure assessment comment
Exposure measures taken near diagnosis may not be representative of the etiologic period.
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
Non-Hispanic whites and "other"
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, race/ethnicity, lactation history
Description of major analysis
Pearson chi-square for differences by case status, p for trend from Mantel chi-square, Kruskal-Wallis and Wilcoxon Rank Sum tests for differences in congener distributions across categories of age and race/ethnicity. International Toxic Equivalents were
Strength of associations reported
Cases had significantly shorter lactation histories. Women of color had generally higher levels of dioxins than non-Hispanic whites. Age and ethnicity-adjusted odds ratios did not differ significantly from one and many estimates were below one. OCDD was an exception [2nd tertile OR 1.22 (95% CI 0.47-3.16); 3rd tertile OR 1.62 (95% CI 0.64-4.12)]Adjustment for lactation did not change results. Stratified results were statistically unstable, with a suggestion that elevated risk for OCDD was among women of color.
Results Comments
While this study is larger than the previous body burden study, it is still too small to investigate effects among subpopulations. Authors note that some of the established breast cancer risk factors were more common among controls than cases. If benign breast conditions are on the causal pathway to invasive cancer, use of women with benign breast conditions as controls limits the ability to observe elevated risk associated with exposure. Exposure measures taken near diagnosis may not be representative of the etiologic period. Authors note that OCDD, for which elevated risk was observed, has a longer half-life than less chlorinated dioxins and may better reflect lifetime and early-life exposure.
Author address
California Department of Health Services, Environmental Health Investigations Branch, 1515 Clay Street, Suite 1700, Oakland, CA 94612, USA. preynold@dhs.ca.gov