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Considerations for data production > Healthy Canadians > 49-HTL: Five-year relative survival rate for colorectal cancerDefinition DefinitionThe ratio of the observed survival for a group of cancer patients five years after diagnosis to the survival that would have been expected for members of the general population assumed to be practically free of that cancer and who have the same main characteristics associated with survival (such as sex, age, area of residence) as the cancer patients. Rationale and notes for interpretationRelative survival is the most widely used method for analyzing the survival of cancer patients in population studies. It provides an objective measure of the proportion of patients dying from the direct or indirect consequences of their disease in a given population. That is, a measure of patient survival corrected for the effect of other independent causes of death. Age standardized relative survival ratios are interpretable as the relative survival ratio that would have occurred if the age distribution of the patient group under study had been the same as that of the standard population. Age standardization controls for a bias that may be introduced by comparing relative survival estimates amongst provinces with different case age distributions. Unless they have been age-standardized to the same population, relative survival ratios from other sources should not be compared with those presented in this analysis. The relative survival rate is influenced by two distinct groups of factors: (1) the severity (stage) of the cancer at the time of diagnosis, and (2) the effectiveness of cancer treatment after diagnosis. While the indicator does not shed light on the relative importance of these two kinds of factors, from the viewpoint of interpreting the indicator, these two factors work in the same direction. For example, an improvement in screening would result in cancers being detected at an earlier stage, where treatments are generally more successful, resulting in better observed survival. And if there had not been a significant change in screening, better observed survival would indicate more effective and successful cancer treatment after diagnosis. This interpretation issue is currently being addressed by the addition of staging data to the cancer registry systems. Cancer staging data indicates how advanced (serious) the cancer is at the time of diagnosis. Prostate, breast, lung and colorectal cancer are reported on because they represent the four most common cancer sites. In particular, lung cancer relative survival rates are reported to inform the public of the poor prognosis of this cancer. The fact that health system interventions with lung cancer are not very successful underscores the need to emphasize preventive strategies. It should be noted that variations in the use of prostate cancer screening (prostate specific antigen or PSA testing) have affected incidence rates of prostate cancer over the past ten years, and this has likely had an impact on relative survival ratios. Technical specifications
Data availability
Considerations for indicator quality and comparabilityComparison with the Canadian age-standardized ratio is recommended. National and provincial results should be reported in a table. 95% confidence intervals should be reported with each estimate. Number of eligible cases and number of deaths in the first five years of follow-up may also be reported. Analysis was conducted using the maximum likelihood method of Estève. Relative survival rates were standardised to the age distribution of eligible patients diagnosed with the specific cancer (National estimates exclude Quebec). Quebec data were not included (..) in the national estimates of five-year relative survival because their method of ascertaining the date of diagnosis of cancer cases differs substantially from that of other provincial cancer registries. Responsibility to produce the dataStatistics Canada |
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