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Cancer Prevalence Methodology

Cancer Prevalence
Short description of Indicator Cancer prevalence: The number of people diagnosed with cancer during a specified time period who were still alive on a given date.
Rationale for measurement Cancer prevalence quantifies the population who are likely to be interacting with the cancer system. It includes both new (incident) and existing cases of cancer, representing a mixture of individuals at different stages of the cancer journey, from the newly diagnosed who are undergoing active treatment to long-term survivors. Cancer prevalence estimates can be used to support and inform current and future planning initiatives, including resource allocation, for healthcare and support services.
Evidence/references for rationale This is a well-established cancer burden indicator, described and reported on by numerous provincial, national and international organizations, including:
Calculations for the indicator Ten year prevalence:
  • Calculated as the number of Ontarians diagnosed with cancer within the previous ten years who were still alive on a given date.
  • A person diagnosed with more than one type of cancer (e.g., breast and colorectal cancer) in that ten-year period will be included in the count for each cancer diagnosed. If a person is diagnosed with more than one of the same cancer (e.g., a person with two colorectal cancers), only one cancer will be included in the prevalence estimate.


  • Calculated for the 4 most common cancers (Prostate [ICD-O-3 code: C61.9], female breast [ICD-O-3 code: C50.0–C50.9], colorectal [ICD-O-3 code: C18.0–C20.9, C26.0] and lung [ICD-O-3 code: C34.0–C34.9]), Ontario, as of January 1, 2017
Standardized Rate Calculation N/A
Unit N/A
Data sources Ontario Cancer Registry, 2018 (Ontario Health [Cancer Care Ontario])
Time Frame 2007-2016
Geographic Scale Provincial
Denominator description N/A
Numerator description N/A
  • Cancers were defined using U.S. Surveillance, Epidemiology and End Results (SEER) Recode definitions: see Cancer definitions using SEER Recode may differ, especially for cancers of the colon and rectum and lung cancer, from definitions in other published analyses.
  • 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"
    • Colon and rectum (ICD-O-3 code C18.0–C18.9, C19.9, C20.9, C26.0): short title “Colorectal"
  • The Ontario Cancer Registry (OCR) does not actively follow cases and so deaths may be missed. This may lead to overestimates of prevalence, especially for longer periods of time.
  • Estimates of prevalence for a ten year period represent a mixture of individuals at different stages of the cancer experience, from the newly diagnosed through to the long-term survivors. Healthcare needs vary across this ten year period and include active treatment, follow-up and treatment for recurrences, and end-of-life or palliative care.
Data availability & limitations Prevalence is shown for cancers diagnosed through 2016, the most recent year for which the Ontario Cancer Registry had received complete data at the time of analysis.