A geographical analysis of breast cancer clustering in southern Ontario: generating hypotheses on environmental influences

Abstract

This article presents the results of spatial analysis of breast cancer clustering in southern Ontario. Data from the Cancer Care Ontario were analyzed using the Scan Statistic at the level of county, with further analysis conducted within counties that were identified as primary clusters at the dissemination area level. The results identified five counties as primary clusters of women diagnosed with breast cancer between 1986 and 2002: Essex (relative risk [RR] = 1.096–1.061; p < 0.001), Lambton (RR = 1.05–1.167), Chatham-Kent (RR = 1.133–1.191), Niagara (RR = 1.228–1.290) and Toronto (RR = 1.152–1.146). The within county analysis revealed several DAs with significantly higher (RR > 3, p < 0.05) rates of breast cancer, and supports our hypothesis that breast cancer risk in southern Ontario may be associated with industrial and environmental (such as pesticides) pollutants. Further research is needed to verify the environmental links within the identified clusters.

Keywords:

• breast cancer
• spatial analysis
• environmental pollution
• southern Ontario

Acknowledgements

This study was supported by the Canadian Breast Cancer Research Alliance (Canadian Institutes of Health Research [CIHR] grant 67161), the Canadian Cancer Society (National Cancer Institute of Canada grant no. 016160), the National Cancer Institute, National Institutes of Health (contract no. N01-PC 65064) to Kevin Gorey, as well as CIHR and Ontario Ministry of Health and Long Term Care investigator awards, and an associated CIHR partnership award to Kevin Gorey and Isaac Luginaah, respectively. Isaac Luginaah was also supported by funds from the Canada Research Chairs Program. The authors gratefully acknowledge the research and assistance was provided by Carole Herbert (Cancer Care Ontario). The authors would like to thank Ms. Karen Vankerkoerle for providing cartographic support. The authors declare they have no competing financial interests.