Taking residential history data provided by a cohort of women with breast cancer and controls in Western New York, and using geographic positioning technology, the researchers showed that the women who developed breast cancer were more likely to have lived closer together at birth and at menarche, a concept called clustering, than women who didn't develop breast cancer.
The findings indicate that there may be something in the environment close to these clusters that influences a woman's breast-cancer risk, said Jo Freudenheim, Ph.D., professor in the Department of Social and Preventive Medicine in the UB School of Medicine and Biomedical Sciences and senior author on the study.
Only a few prior studies have examined these time periods for cancer risk, and none have focused on environmental exposures, she said.
Results of the research were presented on June 21 during an "environmental spotlight session" at the annual meeting of the Society for Epidemiological Research.
"Not too long ago, researchers were looking only at relatively recent environmental exposure, maybe in the last 10 years, when we were studying the relationship of environment to breast-cancer risk," Freudenheim said.
"Recently we've come to understand that breast-cancer risk may be influenced by events early in life. These data support that hypothesis. The next step is to identify where these places are and see if we can identify exposures that explain the clusters."
Freudenheim is principal investigator on a three-year project funded by the U.S. Department of Defense to study the possible link between breast cancer and early environmental exposure to potential carcinogens. The current presentation represents some of the first findings from that research.
The project piggybacks on Freudenheim's ongoing case-control study of breast cancer in Erie and Niagara counties in Western New York, which involves 1,170 women with recently diagnosed breast cancer and 2,116 healthy women. Of this total, 1,073 women who were born in either of the two counties and had provided the address of their residence at birth became the focus of the current research.
UB geographers and epidemiologists are entering residential data into a computerized mapping program, along with the location of steel mills, chemical factories, gasoline stations, toxic-waste sites and other industrial sites in existence in the two counties between 1918-80. They then will calculate the distance between these sites and the women's homes at the time of birth and menarche (date of first menstruation), and compare this information for the participants with and without cancer.
These early data revealed the greatest clustering of cancer cases at the time of menarche, said Daikwon Han, a graduate student in geography who is first author on the study. Some clustering also was evident for place of birth, he said, but there was no clustering effect for the women at the time they first gave birth
"Researchers think the breast tissue may be more sensitive to environmental insults in childhood and that exposures early in life could increase the risk of breast cancer in adulthood," said Freudenheim. "After a first birth, a woman's breast cells may become more resistant to environmental insults. This project is a really good chance to learn more about the role of environmental exposures during infancy and menarche on health and disease later in life."
Also contributing to this research were John Vena, Ph.D., professor; Jing Nie and Matthew Bonner, graduate students, and Dominica Vito, project administrator, all in the UB Department of Social and Preventive Medicine. Peter Rogerson, Ph.D., professor in the Department of Geography in the UB College of Arts and Sciences, also worked with Han.
The research was supported by a grant from the Department of Defense Breast Cancer Research Program and from the National Institutes of Health.