摘要：Colorectal cancer (CRC) remains one of the most common causes of cancer-related morbidity and mortality in North America. (1) The incidence of CRC has been decreasing in the United States (US) since the 1990s and in Canada since the early 2000s. (1,2) However, the reduction in CRC-induced morbidity and mortality has not been uniform among all groups. In the US, there has been lower CRC mortality reduction among individuals in lower income groups. (3) Higher CRC incidence among individuals living in areas of lower socio-economic status (SES) has also been reported in the US. (4) Many of the health care disparities observed there have often been attributed to the lack of access to universal health care. The framework of fundamental social causes ("resources that can be used to avoid risks or to minimize the consequences of disease once it occurs" (5) including "money, knowledge, status and availability of social support" (3)) predicts that when a new resource becomes available (e.g., screening for cancer), it will be more readily accessed by people who already have resources, leading to earlier and more rapid reduction in disease incidence and mortality in that group. This framework may be used to understand and predict gaps and disparities in health outcomes. It is important to determine whether Canadian provinces are able to minimize such expected disparities.
In addition, in order to target efforts to decrease CRC morbidity and mortality, it is important to determine the groups with the worst CRC outcomes. There are limited data on variation (or lack of it) in CRC outcomes among different socio-economic groups in Canada and no published data on spatial variation of CRC incidence by neighbourhood of residence. Studies on the association of SES and CRC incidence have been limited to those from Ontario between the mid-1980s and mid-1990s. (6,7) Canada is a country with a universal health care plan in each province and population-based CRC screening programs in most provinces, which should lead to lower disparities. However, we recently reported an increase in CRC mortality among individuals residing in lower income areas in Manitoba, one of the central Canadian provinces. (8) This could be due to biological differences in CRC, environmental differences (e.g., diet), delayed diagnosis of CRC or worsening survival after CRC diagnosis (due to inadequate treatment or response to treatment), or multiple factors. The implications for public health are vastly different for delayed diagnosis, biological differences, and worsening survival.
