|Short description of Indicator
||Five-year relative survival ratio: the proportion of people alive five years after their diagnosis, divided by the survival expected among people of the same age, sex, and time period in the general population.
|Rationale for Measurement
||Relative survival compares the survival experience of individuals with cancer to that of the general population of the same age and sex. It shows the extent to which a diagnosis of cancer shortens a life span. As an indicator of both disease severity and prognosis, relative survival is a popular indicator for several aspects of cancer control, including monitoring progress in treatment and early detection (i.e., screening).
|Evidence/references for rationale
||This is a well-established cancer burden indicator, described and reported on by numerous provincial, national and international organizations, including:
Additional evidence supporting the utility of this measure is described in:
- Dickman PW, Adami HO. Interpreting trends in cancer patient survival. J Intern Med. 2006; 260(2):103–17.
Mariotto AB, Noone AM, Howlader N, Cho H, Keel GE, Garshell J, et al. Cancer survival: an overview of measures, uses, and interpretation. J Natl Cancer Inst Monogr. 2014; 2014(49):145-86.
|Calculations for the indicator
||Five-year relative survival ratio (age-standardized):
|Standardized Rate Calculation
||Ontario Cancer Registry, 2016 (Cancer Care Ontario)
- On Oct. 29, 2014, CCO’s Ontario Cancer Registry Information System (OCRIS) was formally decommissioned and replaced with the new Ontario Cancer Registry (OCR). The new registry brings the OCR in line with current Canadian and U.S. standards for tracking cancer incidence. The OCR now conforms to specific standards as set out by the National Cancer Institute’s Surveillance, Epidemiology and End Results (NCI SEER) program for counting multiple primary cancer sites, which most Canadian provinces and U.S. states now use. The adoption of specific NCI SEER standards with the new OCR has resulted in an increase in the incidence number of certain types of cancer reported in Ontario. To mitigate the impact of this change on survival estimates, relative survival estimates are based on one cancer case per SEER recode site group, per person as noted in the calculations section above.
- Cancers were defined using U.S. Surveillance, Epidemiology and End Results (SEER) Recode definitions: see http://seer.cancer.gov/siterecode/icdo3_dwhoheme/index.html. Cancer definitions using SEER Recode may differ, especially for cancers of the colon and rectum and lung cancer, from definitions in other published analyses of survival.
- For most cancer types (except urinary bladder and kidney), the full site grouping name outlined by the SEER site recode variable definitions was used. Short titles for certain cancers, however, were, used for graphing purposes. Cancer types for which short titles were displayed are as follows:
- Lung and bronchus (ICD-O-3 code C34.0–C34.9): short title “Lung”
- Melanoma of the skin (ICD-O-3 code C44.0 with histology codes 8720–8790): short title “Melanoma”
- Corpus and uterus, NOS (ICD-O-3 code C54.0–C54.9, C55.9): short title “Uterus”
- Colon and rectum (ICD-O-3 code C18.0–C18.9, C19.9, C20.9, C26.0): short title “Colorectal”
- Urinary bladder (ICD-O-3 code C67.0–C67.9): short title “Bladder”
- Kidney and renal pelvis (ICD-O-3 code C64.9, C65.9): short title “Kidney”
- Age-standardizing five-year relative survival ratios and conditional five-year relative survival ratios allows for comparison across time periods and jurisdictions by adjusting for differences in the age-distributions of the populations of interest.
- Due to changes to the Ontario Cancer Registry, which were implemented for cases diagnosed in 2010 and beyond, comparisons of the Ontario five-year survival estimates for 1999-2003 and 2009-2013 should be interpreted with caution. For the LHIN estimates, comparisons over time should not be made.
- Relative survival is a useful population-based indicator of the burden of cancer and the variation in severity of different types of cancer. It does not necessarily reflect a person’s chance of surviving for a given time after diagnosis.
- The Ontario Cancer Registry does not actively follow cases and so deaths may be missed. This, and the exclusion of individuals whose date of diagnosis is their date of death, may lead to overestimates of survival.
- Relative survival estimates can be biased and can over- or under-estimate survival if there is a mismatch between the life table and the cancer patient cohort.1 In some cases, age-standardized relative survival estimates in excess of 100% are possible, suggesting that survival in the cancer patient cohort was higher than the expected survival in a comparable group from the general population, as measured by national life tables. This can happen when information on deaths is missing in the registry or when life tables do not reflect the background mortality experience of the population from which the cancer patient originated, or when cancer patients are successfully treated for their cancer and other comorbidities and, as a result, adopt a healthier lifestyle.
Ellison LF. Estimating relative survival for cancer: An analysis of bias introduced by outdated life tables. Health Rep 2014; 25:13-19.
|Data availability & limitations
||Five-year relative survival ratios are shown through 2013, the most recent year for which the Ontario Registry has received complete data at the time of analysis.