Associations between community income and cancer survival in Ontario, Canada, and the United States.

PURPOSE: The objectives of this study were as follows: (1) to compare the magnitude of the association between socioeconomic status (SES) and cancer survival in the Canadian province of Ontario with that in the United States (U.S.), and (2) to compare cancer survival in communities with similar SES in Ontario and in the U.S.
METHODS: The Ontario Cancer Registry provided information about all cases of invasive cancer diagnosed in Ontario from 1987 to 1992, and the Surveillance, Epidemiology and End Results Registry (SEER) provided information about all cases diagnosed in the SEER regions of the U.S. during the same time period. Census data provided information about SES at the community level. The product-limit method was used to describe cause-specific survival. Cox proportional hazards models were used to describe the association between SES and the risk of death from cancer.
RESULTS: There were significant associations between SES and survival for most cancer sites in both the U.S. and Ontario, but the magnitude of the association was usually larger in the U.S. In the poorest communities, there were significant survival advantages in favor of cancer patients in Ontario for many disease groups, including cancers of the lung, head and neck region, cervix, and uterus. However, in upper- and middle-income communities, there were significant survival advantages in favor of the U.S. for all cases combined and for several individual diseases, including cancers of the breast, colon and rectum, prostate, and bladder.
CONCLUSION: The association between SES and cancer survival is weaker in Ontario than it is in the U.S. This is due to a combination of better survival among patients in the poorest communities and worse survival among patients in the wealthier communities of Ontario relative to those in the U.S.