Abstract
Population-based case-control study in Poland to identify occupational and environmental risk
factors for breast cancer
Beata Pepłońska1, Montserrat Garcia-Closas2, Louise Brinton2, Aaron Blair2, Neonila SzeszeniaDąbrowska1, Jolanta Lissowska3
Department of Occupational and Environmental Epidemiology, Institute of Occupational Medicine, Łódź,
Poland
2
Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, USA
3
Department. of Cancer Epidemiology and Prevention. Cancer Center and M. Sklodowska-Curie Institue of
Oncology, Warsaw, Poland
1
Context: Breast cancer is the most common cancer in women in the world. As many as 1,050,346
incident breast cancer cases were identified in 2000 (Globocan, 2000). Age over 50, breast cancer in first
degree relatives, high socio-economic status, exposure to ionizing radiation during adolescence,
menopausal obesity, late pregnancy, early menarche, and late menopause are among the most important
established risk factors. However, according to various authors, as much as 53-75% of breast cancer cases
are unexplained by those agents. Both incidence and mortality rates are higher in females in more
developed as compared to less developed countries. This observation raises hypotheses regarding the
potential etiologic role of occupational and environmental factors. For instance, an increased incidence or
risk of death from breast cancer has been observed in some studies among teachers, nurses and physicians,
managers, beauticians and hairdressers, chemists, telephone and telegraph operators, and workers in the
pharmaceutical and chemical industry. Some epidemiological studies indicate that breast cancer incidence
might be related to occupational exposures to electromagnetic fields, ionizing radiation, low physical
activity, organic solvents, and selected pesticides. However, given inconsistent study results and
methodological weaknesses (imprecise classification of exposure, low response rate, uncontrolled
confounding), no definite conclusions can be drawn. Polymorphisms in genes responsible for metabolizing
occupational and environmental chemicals could also affect the risk of breast cancer.
Objective: To assess occupational and environmental risk factors for breast cancer in a total series of
population-based cases and within groups defined by relevant genetic markers.
Design, Setting and Participants: A population-based case-control study was started in February
2000 in two areas in Poland (Warsaw and Łódź). Cases consisted of female residents of Warsaw and Łódź
aged 20-74 with newly diagnosed breast cancers that were cytologically or histologically confirmed.
Controls were randomly selected within five-year age groups using the Polish Electronic System of
Population Evidence. Demographic and other risk factor data were collected using a structured
questionnaire. Lifetime work histories were collected, including job title, start and stop dates and work
activities, exposure to chemicals, and physical activity at work. Medical information for cases was
abstracted from medical records. Blood specimens, mouth wash collections, 12-hour urine samples, and
anthropometric measurements were obtained from every subject after written informed consent. Paraffin
blocks of tissue samples and alcohol preserved tissue samples were also collected. In Warsaw, additional
procedures applied: physical activity monitoring, vacuum bag collection, and fresh tissue collection.
Quality control of data were verified by re-abstracting data from medical records for 10% of cases and
conducting a short telephone re-interview for 10% of the subjects. The records of the Regional Cancer
Registry were reviewed to assess the completeness of case ascertainment. Biologic samples were sent to
the United States, where a variety of assays for genetic and environmental risk factors will be conducted.
Results: After three years of study, 3,042 incident cases have been identified. Approximately 2,379
(81%) cases have agreed to participate and indicated by written consent in which parts of the study they
would participate. Lower response rates occurred in controls–70%. Among women who agreed to
participate, 83% of the cases and 90% of controls provided a blood sample.
Conclusions: This complex study has successfully enrolled a large number of breast cancer cases and
controls with high response rates. The availability of detailed exposure information and biological
specimens should allow us to evaluate a large number of etiological questions relevant to breast cancer.
Ethical Issue: Subjects who participate in the study will not be provided with individual results of the
analyses performed. This data has no diagnostic or therapeutic meaning for study participants. This issue
was explained to the participants both in the invitation letter and the consent form.