Disparities in cancer survival between Indigenous and non-Indigenous adults in Canada: Results from linkage of the 1991 Census Mortality Cohort and the Canadian Cancer Registry

Diana WITHROW, University of Toronto, Canada
WITHROW D. 1,2 , MARRETT L. 1,2 , TJEPKEMA M. 3 , NISHRI E. 1 , POLE J. 2,4

1 Aboriginal Cancer Control Unit, Cancer Care Ontario, Toronto, Canada
2 Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
3 Health Analysis Division, Statistics Canada, Ottawa, Canada
4 Pediatric Oncology Group of Ontario, Toronto, Canada

PURPOSE: A lack of ethnic identifiers in Canadian cancer registries limits understanding of cancer burden in ethnic subgroups. We use a census-registry linkage to compare cancer survival of First Nations, Métis and non-Indigenous adults in Canada.
METHODS: The cohort comprises a 15% sample of the Canadian population derived from the 1991 Long Form Census. Cohort members are followed for cancers and deaths from 1992 to 2009. We measured site-specific age-standardized 5-year relative survival using age-, sex-, ethnicity- and calendar time-specific life tables. Flexible parametric modeling was used to estimate the excess mortality rate ratio (EMRR) for First Nations (FN) and Métis compared to their non-Indigenous peers.
RESULTS: Cancer survival was significantly poorer for FN than for non-Indigenous Canadians for 9 of 15 cancers examined. EMRRs ranged from 1.00 (95%CI: 0.68-1.47) for multiple myeloma to 2.39 (95%CI: 1.63-3.50) for prostate cancer. Taking rurality and income into account reduced EMRRs slightly but they remained elevated for 7 out of 15 cancers. Among Métis, there was a consistent trend toward poorer survival for all 4 cancers examined, with the greatest disparity for prostate cancer.
CONCLUSIONS: Indigenous people in Canada experience poorer survival than their non-Indigenous peers, even after accounting for differences in income and rurality, supporting the need for: 1. additional research to understand why; 2. additional investments in culturally appropriate initiatives to reduce cancer burden; and 3. creation of databases for ongoing monitoring of cancer burden. This will require novel methodologies and appropriate data sharing, collaboration and capacity-building arrangements with Indigenous organizations.
FUNDING SOURCE: Canadian Institutes for Health Research