It is known that the socioeconomic status (SES) of the patient is associated with cancer survival in the United States. The purpose of this study was to determine whether the association between SES and survival is also present in Canada, a society with a comprehensive, universal, health insurance program.
A population-based cancer registry was used to identify the 357,530 cases of invasive cancer diagnosed in the Canadian province of Ontario between 1982 and 1991. Information from the 1986 Canadian census was linked to the registry and used to describe the SES of the area in which each patient resided. Cox regression was used to describe the association between median household income and survival while controlling for age, sex, and the region in which the patient resided. The Cox model was fitted in a competing risk framework to assess the association between income and the probability of specific causes of death.
Lung cancer and cancers of the head and neck region were relatively more common in poor-income communities, and cancers of the breast, CNS, and testis were relatively more common in richer communities. A strong and statistically significant association between community income and survival was observed in cancers of the head and neck region, cervix, uterus, breast, prostate, bladder, and esophagus. Smaller, but significant associations were seen in cancers of the lung and rectum. No significant association between community income and survival was observed in cancers of the stomach, colon, pancreas, or ovary. Analysis of the cause of death showed that community income is associated both with the probability of death from cancer and with the probability of death from other causes.
Although Canada's health care system was designed to provide equitable access to equivalent standards of care, it does not prevent a difference in cancer survival between rich and poor communities.