Environment and Breast Cancer: Science Review

Evidence From Humans
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The link between the insecticide heptachlor epoxide, estradiol, and breast cancer
Cassidy, R. A., Natarajan, S., Vaughan, G. M. Breast Cancer Research and Treatment. 2005. 90:1, 55-64.
Topic area
Environmental pollutant - Pesticide, heptachlor epoxide, oxychlordane, DDE
Study design
Hospital based case-control
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number of Controls
Controls: 17
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
34 women seen for surgical evaluation of a palpable breast mass or mammographic abnormality at Brooke Army Medical Center from 1994-1998
Comment about participation selection
Small number of subjects. Comparison group referred for breast biopsy is not representative of a normal population.
Exposure Investigated
Exposures investigated
Heptachlor epoxide, oxychlordane, DDE in breast adipose tissue extracted by sparging, divided in quartiles
Exposure assessment comment
Single measure at time of diagnosis.
Statistical Analysis
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, body weight, height, body mass index, age at menarche, gravidity, cumulative lactation time, breast adipose organochlorine concentration, history of oral contraceptive use, estrogen replacement therapy, family history of breast cancer were considered
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
Binary multiple logistic regression
Strength of associations reported
Linear dose-response relationship is observed for concentration of heptachlor epoxide in quartiles and breast cancer. For the highest compared with lowest quartile, age-adjusted relative risk = 3.2 (95% CI 1.1-9.2), p trend < 0.01. Oxychlordane level is higher in malignant than benign tissue, but the difference is not statistically significant at p < 0.05, and relative risk is not reported. DDE level is non-significantly higher in malignant tissue than benign.
Results Comments
Authors state that cyclodienes (chlordane, heptachlor, aldrin) are metabolized to the epoxides oxychlordane (OC) and heptachlor epoxide, and dieldrin. Serum levels of HE and OC have declined little in humans, probably because of inhalation in homes treated for termites in 1950s to 1988. Semivolatiles (HE and OC) may be lost in the laboratory extraction techniques used in other studies. No significant differences between women with benign and malignant tissue are seen for many established breast cancer risk factors in this small sample. Authors note that HE is related to body mass index and high fat diet and inversely with lactation.
Author address
ToxFree, Inc., Tell City, IN 47586, USA. rcassidy@dcci.com