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Environmental Polychlorinated Biphenyl Exposure and Breast Cancer Risk: A Meta-Analysis of Observational Studies
Zhang, J., Huang, Y., Wang, X., Lin, K., Wu, K. PLoS One. 2015. 10:11, e0142513.
Topic area
Environmental pollutant - PCBs
Study design
Meta-analysis
Funding agency
National Natural Science Foundation of China
Study Participants
Number of Cases
6,088 cases in all studies combined
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Number of Controls
Controls: 6,778 controls in all studies combined
Country where study was conducted
This meta-analysis was conducted in China and revi
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Twenty-five case-control or cohort studies published between 1994-2013 with biological measurement of PCB levels, at least 50 female breast cancer cases, and non-overlapping study populations.
Comment about participation selection
Study quality was evaluated using the Newcastle-Ottawa Scale. Eight of the case-control studies were given lower ratings because of 'potential selection biases or use of hospital controls'.
Exposures investigated
Plasma, serum, or adipose tissue concentration of PCB congeners. Groupings were based on those proposed by Wolff et al. 1997, as follows: Potentially estrogenic (Wolff et al. 1997 group 1): 44, 52, 101, 177, 187, 201 Potentially anti-estrogenic and immu
Breast cancer outcome investigated
Primary incident breast
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.
Most studies adjusted for age, BMI, family history of breast cancer, history of benign breast disease, age at menarche, and lactation. Nineteen of 25 studies accounted for lipids, though the method varied (some used lipid-adjusted serum concentrations, ot
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
No
Strength of associations reported
Meta-OR for highest vs lowest category of total PCB exposure: OR 1.09 (95% CI 0.97-1.22)
Meta-OR for highest vs lowest category of potentially estrogenic PCBs (Group I): OR 1.10 (95% CI 0.97-1.24)
Meta-OR for highest vs lowest category of potentially antiestrogenic and immunotoxic, dioxin-like PCBs (Group II): OR 1.23 (95% CI 1.08-1.40)
Meta-OR for highest vs lowest category of phenobarbital, CYP1A and CYP2B inducers, biologically persistent PCBs (Group III): OR 1.25 (95% CI 1.09-1.43)
Results Comments
Retrospective studies yielded a greater combined OR than did prospective studies across all PCB exposure categories.
Author address
Department of Preventive Medicine, Shantou University Medical College, Shantou, Guangdong, China.
Reviewers Comments
The effect estimate for "total PCB exposure" appeared to vary across studies; for example, from Cohn et al., 2012, the "total PCB exposure" OR was for the ratio PCB 203/ (PCB 167 + PCB 187). In Gatto et al., on the other hand, the "total PCB exposure" OR was based on analysis of total PCBs in serum, based on a commercial mixtures Aroclor 1242 and 1260. The authors did perform several sensitivity analyses, but none of these stratified the analysis by study quality ("high" vs "moderate").
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