Environment and Breast Cancer: Science Review

Evidence From Humans
Print this page
Case-control study of occupational categories and breast cancer risk in Thailand
Ekpanyaskul, C., Khuhaprema, T., Wiangnon, S., Sangrajrang, S. Asian Pac J Cancer Prev. 2010. 11:3, 793-7.
Topic area
Environmental pollutant - Occupation
Study design
Population based case-control
Funding agency
Not reported
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analyses by menopausal status
Number of Controls
Controls: 516
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Cases were all new incident breast cancer patients in 3 hospitals in 2002-2004. Controls were randomly selected from healthy women who visited patients (with diseases other than breast or ovarian cancer) at those hospitals and matched on 5 year age groups and geographical area.
Comment about participation selection
Control group including hospital visitors may not be representative of the population from which the cases arose. Women referred to or visiting patients at the three hospitals who were never employed in a given job sector were the study's reference group.
Exposure Investigated
Exposures investigated
Lifetime occupational history questionnaire of 3 major job categories by in-person interview. Only occupations which were held for more than 1 year were included in the analyses.
Exposure assessment comment
Because there are 516 cases, and a total of 621 cases had ever worked in each major job category, there are some cases who worked in more than one occupation. Although results show no association between breast cancer risk and number of occupations in work life, it opens the possibility of unevenly weighted exposures, especially in the ever/never analysis.
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.
Age, BMI, regular exercise, smoking, family history of breast cancer, use of birth control pill
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
Compared to women in all other occupational groups:
Production/related workers, transport equipment operators/laborers: OR 1.41 (95% CI 1.02-1.97)
Production/related workers, transport equipment operators/laborers, 1-10 years lag: OR 3.40 (95% CI 1.22-9.47)
>5 years production/related workers, transport equipment operators/laborers: OR 1.44 (95% CI 1.01-2.09)
>5 years service workers: OR 1.50 (95% CI 1.00-2.24)
Results Comments
This study considered many additional job titles. We focus on (1) significant positive associations (2) if a particular job or sector was significantly associated with breast cancer in at least one study, we report results from all other studies that considered that sector, regardless of significance. It is important to note that job coding criteria generally differed across studies.
Author address
Department of Preventive and Social Medicine, Faculty of Medicine, Srinakharinwirot University, Khon Kaen, Thailand. sulee@health.moph.go.th
Reviewers Comments
Vague job classifications limit interpretation of findings. The authors state that the lack of association seen between agriculture and service sectors and breast cancer is inconsistent with other studies of occupation and breast cancer risk in Thailand.