Environment and Breast Cancer: Science Review

Evidence From Humans
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XPD Lys751Gln increases the risk of breast cancer
Samson, M., Singh, S. S., Rama, R., Sridevi, V., Rajkumar, T. Oncol Lett. 2011. 2:1, 155-159.
Topic area
Environmental pollutant - PAHs
Study design
Hospital-based case-control
Funding agency
Chennai Willingdon Corporate Foundation
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Number of Controls
Controls: 20
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Cases and controls were South Indian women. Cases had histologically confirmed breast cancer and no previous cancer treatment, while controls were diagnosed with a breast disease other than cancer (e.g. fibroadenoma). Control tissue was removed from 'normal' area, not from the pathological (e.g. fibroadenomatous) tissue. Healthy controls were also recruited, but considered only in the polymorphism analysis (not the PAH-DNA adduct analysis).
Comment about participation selection
Case and fibroadenoma/fibroadenosis control selection is not well described and no information given about characteristics of the study population (not even age).
Exposure Investigated
Exposures investigated
PAH-DNA adducts & XPD polymorphisms (Lys/Lys, Gln/Gln, and Lys/Gln) measured in breast biopsy samples.
Exposure assessment comment
XPD is involved in the nucleotide excision repair (NER) pathway.
Breast cancer outcome investigated
Primary incident breast cancer
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.
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked Yes. No, if not.
Strength of associations reported
PAH adduct score of >3 compared to ≤ 3 PAH adducts:
OR 5.12 (95% CI 1.65-15.8)

XPD genotypes, among women with PAH adduct score ≤ 3 (Ref = Lys/Lys genotype):
Gln/Gln (4 cases, 4 controls): OR 0.75 (95% CI 0.13-4.2)
Lys/Gln (5 controls): OR 1.80 (95% CI 0.40-7.9)

XPD genotypes, among women with PAH adduct score > 3 (Ref = Lys/Lys genotype):
Lys/Gln (2 controls): OR 1.90 (95% CI 0.28-12.8)
Results Comments
Only 5 total controls with PAH adduct score > 3. No controls carried Gln/Gln polymorphisms and >3 adducts.
Author address
Department of Molecular Oncology, Cancer Institute (WIA), Adyar, Chennai 600020, India.
Reviewers Comments
The study is very small for evaluation of an interaction. The lack of descriptive information about the study population (e.g. age range) and the complete lack of control for confounding make it difficult to interpret these results.