The Ontario Cancer Registry, which is maintained by Ontario Health (Cancer Care Ontario), is the main data source for this report. The registry’s goals are to collect, analyze and disseminate timely and high-quality information describing cases of cancer diagnosed among Ontario residents. The female and male sex terms used in this report refer to the sex that is recorded in the Ontario Cancer Registry.

The registry is a dynamic database; new case information and updates to past cases may be added throughout the year. Consequently, the results of analyses vary based on when the data are extracted from the registry. The data in this report were extracted in December 2020 (mortality) and March 2021 (incidence, survival and prevalence).

Ontario Cancer Registry records are created using data collected for purposes other than cancer registration. This information comes from various administrative databases, laboratory reports and clinical records. Four primary sources are used to generate case records in the registry:

• provincial pathology reports from Ontario's public hospital laboratories and private laboratories
• activity-level reporting database, containing data from Ontario's 14 regional cancer centres and their associated hospitals, for selected systemic therapy and all radiation treatment
• admission and discharge information from the Canadian lnstitute of Health lnformation's hospital abstracting databases (Discharge Abstract Database, National Ambulatory Care and Reporting System)
• cause-of-death data from the Office of the Registrar General for Ontario within the Ministry of Government and Consumer Services

Safeguarding confidential information is a guiding principle for Ontario Health (Cancer Care Ontario). All activities – from the initial registration of a new cancer case in the Ontario Cancer Registry, through to research and reporting – are governed by the Personal Health Information Protection Act, 2004.^[1] This Ontario law governs the collection and use of data, and the disclosure of personal health information. The act designates Ontario Health as a prescribed entity and authorizes the organization to collect, use and disclose personal health information for the purposes of managing and planning Ontario's health system. See our Statement of Information Practices for details.

Data Quality

Death certificate only and microscopically confirmed cases

Table A.1 shows the percentage of cases in the Ontario Cancer Registry diagnosed based on a death certificate only and the percentage microscopically confirmed.

Overall, 1.3% of cases diagnosed in 2018 were death certificate only. The percentage ranged from a low of 0.1% for thyroid cancer and melanoma to a high of 3.4% for pancreatic cancer.

For all cancers combined, 90.9% of cases were microscopically confirmed. This falls slightly below the Surveillance, Epidemiology and End Results Program's recommendation of at least 93% of cases microscopically confirmed.^[2] The percentage microscopically confirmed varied from a low of 55.3% for liver to a high of 99.2% for thyroid cancer.

Symbol: ** Suppressed due to small case count (count less than 6).

Analysis by: Ontario Cancer Registry, Ontario Health (Cancer Care Ontario)
Data source: Ontario Cancer Registry (March 2021), Ontario Health (Cancer Care Ontario)

Incidence-to-mortality ratio

The age-standardized incidence-to-mortality ratio identifies areas of under-coverage within a registry. The incidence-to-mortality ratio for the Ontario Cancer Registry for 2018 was 3.2:1 (Table A.2). This ratio meets the Canadian Partnership Against Cancer's recommended ratio of at least 2.3:1 ^[2], with variation by cancer type. An incidence-to-mortality ratio below the recommended level may indicate incomplete registration of cases.

Note: I:M ratio is the ratio of the age-standardized incidence rate to the age-standardized mortality rate.
Abbreviation: l means incidence and M means mortality.

Analysis by: Surveillance, Ontario Health (Cancer Care Ontario)
Data source: Ontario Cancer Registry (incidence (March 2021) and mortality (December 2020), Ontario Health (Cancer Care Ontario)

Data element completeness

All the data quality indicators met the minimal requirements from the Canadian Cancer Registry guideline, which is the Gold (i.e., highest) certification standard of the North American Association of Central Cancer Registries, and the Surveillance, Epidemiology and End Results Program guideline:

• Stage capture rates overall and for collaborative staging achieved the provincial target of 90% for breast, prostate, colorectal, lung and cervical cancers in 2018.
• There were no cases missing information about "age at diagnosis," "age at death" or "sex," thereby meeting the North American Association of Central Cancer Registries’ Gold standard of a maximum of 2% or less. Furthermore, 0.01% of cases were listed as "alive with current age over 100" and 0.005% cases were listed as "dead" with missing death date.
• Postal codes were missing for 1.4% of the cases, which is under the 5% Canadian Cancer Registry’s threshold for this indicator.
• The 1.9% percent of cases with unknown primary (C80.9) also met the less than 2.3% threshold of the Surveillance, Epidemiology and End Results Program standard.

ln 2018, 87.4% of discrete synoptic cancer pathology reports had all mandatory elements complete in accordance with the College of American Pathologists electronic Cancer Checklists.

There are no standards for the average number of sources or notifications per case, or for the percentage of cases with unknown morphology. Cases with a greater number of supporting data sources or notifications are assumed to be considered more complete and credible. The high percentage of unknown morphology raises some concern about data quality and data collection. Table A.3 presents other data quality measures related to completeness of Ontario Cancer Registry case registration.

Symbols:

†Histology range 8000 to 8005 (Not otherwise specified)
‡For lung, female breast, colorectal, cervical and prostate cancers only

Notes:

• For all malignant cases and in situ bladder.
• Total number of cases is 84,817 and represents 81,224 people.

Analysis by: Ontario Cancer Registry, Ontario Health (Cancer Care Ontario)

Data source: Ontario Cancer Registry (March 2021), Ontario Health (Cancer Care Ontario)

Population Data

The population used in this report for age standardization is the 2011 Canadian Standard population (Table A.4), which is based on the 2011 Statistics Canada census.

Cancer Care Ontario surveillance reports published before 2016 used the 1991 Canadian Standard population. Therefore, comparing age-standardized rates in this report with the rates in earlier reports is not recommended.

The 1991 standard population is no longer appropriate because the population age structure has changed considerably since then. Using the 2011 standard population results in age-standardized rates that are closer to the crude rate (i.e., rate unadjusted for age distribution).

Except where otherwise noted, population data used in denominators for cancer projections are from the Ontario Ministry of Finance (spring 2021 release).^[3]

Note: Postcensal estimates are based on the 2011 census counts adjusted for census net undercoverage (including adjustment for incompletely enumerated lndian reserves) and the components of demographic growth that took place since that census. lntercensal estimates use counts from 2 consecutive censuses adjusted for census net undercoverage (including incompletely enumerated lndian reserves and postcensal estimates).

Data source: Statistics Canada. Table 17-10-0005-01 – Estimates of population, by age group and sex for July 1, Canada, provinces and territories, annual (persons unless otherwise noted)

Cancer Site Grouping

The Ontario Cancer Registry codes cancer cases using the third edition of the International Classification of Diseases for Oncology (ICD-O-3).^[4] Deaths in the cancer registry are based on the 10th edition of the International Classification of Diseases and Related Health Problems (ICD-10).^[5]

In this report, cancer sites are grouped according to the Surveillance, Epidemiology and End Results Program’s recode systems, with some exceptions.^[6] In these exceptions, the cancer groupings were redefined to be more clinically relevant or to align with definitions used by other cancer surveillance systems.

The full list of cancer definitions and groupings used in this report are in Table A.5.

Abbreviations: ICD-O-3 means International Classification of Disease for Oncology, Third Edition.

Notes:

• Histology types 9590 to 9989 (leukemias, lymphomas and hematopoietic diseases), 9050 to 9055 (mesothelioma) and 9140 (Kaposi sarcoma) are excluded from other specific organ sites.
• Histology types 8720 to 8774 (mucosal melanoma) are excluded from the following sites (and selected subsites): colorectal, ovary, uterine, cervix, prostate, testis, and oral cavity and pharynx.

Abbreviations: ICD-10 means International Statistical Classification of Diseases and Related Health Problems, Tenth Revision.

Non-Melanoma Skin Cancer

Data in this report exclude cases of basal cell and squamous cell carcinoma of the skin, the most common types of non-melanoma skin cancer.

These tumours are generally not life-threatening and are treated in outpatient settings. Although these cases are captured in pathology reports, their large number poses a challenge for data capture and quality assurance by the Ontario Cancer Registry, which is a requirement for meaningful surveillance.

Cancer Stage at Diagnosis

Cancer staging is essential for quality care. Stage data are vital for:

• evaluating the effectiveness of screening and treatment programs
• analyzing survival
• research into new treatments
• resource planning for healthcare management

The tumour–node–metastasis (TNM) system is the most widely used classification system for stage at diagnosis. It is recognized as the international standard for describing the anatomy extent of cancers. TNM definitions, now in their eighth edition, are maintained by the Union for International Cancer Control and the American Joint Committee on Cancer. The stage data for 2018 in this report are based on the eighth edition of TNM^[7], while prior years use collaborative stage, which is based on the seventh edition of TNM.^[8] See Recent Changes in Cancer Staging, Coding and Case Creation Standards for more information.

Collaborative staging (2010 to 2017 years of diagnosis) was a staging approach used by central cancer registries. Collaborative staging brought together the principles of the following:

• National Cancer Institute’s Surveillance, Epidemiology and End Results Program Summary Stage
• TNM categories and stage groupings
• Surveillance, Epidemiology and End Results extent of disease coding structure

Most of the collaborative staging data items were traditionally collected by some cancer registries. These items included tumour size, extension, lymph node status and metastatic status. Other data, such as site-specific or histology-specific factors (e.g., Gleason score and receptor status), were specific to collaborative staging. The data were used to derive the "best stage" grouping consistent with the American Joint Committee on Cancer Staging Manual (in its eighth edition).^[7]

Ontario Cancer Registry staging values for invasive cancer range from stage 1, which means the disease is in the early phase, to stage 4, which means the cancer has spread (or metastasized) to other organs or places in the body. An "unknown stage" is the result of limited stage workup, limited documentation in the person's health record or both. "Not staged" means no attempt at staging has taken place.

Starting with cases diagnosed on January 1, 2005, the Ontario Cancer Registry phased in various versions of collaborative staging by reporting selected cancer type and hospital (see the list of contributing hospitals and regional cancer centres below). Collaborative staging was fully implemented for breast, lung, colorectal and prostate cancers in 2010; for ovarian, uterine and cervical cancers, and melanoma in 2011; and for thyroid cancer in 2013.

Approximately 8% to 16% of breast, colorectal, lung and prostate cancer cases in the Ontario Cancer Registry are missing information on stage at diagnosis and are therefore excluded from this analysis. Stage at diagnosis may be missing due to inadequate supporting information in someone’s medical record to support a definitive stage at the time of diagnosis. Stage distributions may not be the same for the cases with missing data.

RECENT CHANGES IN CANCER STAGING, CODING AND CASE CREATION STANDARDS

Changes in coding and case creation standards implemented in 2018 provide cancer registries with a standard set of rules to follow when coding and counting distinct cancers.

• The 2018 Surveillance, Epidemiology and End Results Solid Tumor Coding Rules replaced the 2007 Surveillance, Epidemiology and End Results Multiple Primary and Histology Coding Rules for cases diagnosed from January 1, 2018, onward in the Ontario Cancer Registry. While this update has not resulted in significant changes in incidence for overall cancer sites, there have been changes to some subtypes and histology codes.
• With the new coding rules, ambiguous terminology (e.g., “with features of”) is no longer used to determine a subtype or histology code. As a result, the prevalence of histological subtypes that have been affected by the new rules may appear to have decreased in 2018. However, this is not a true decrease because the 2018 Surveillance, Epidemiology and End Results Solid Tumor Coding Rules have grouped some subtypes under 1 histology code. One of the sites where this 2018 rule has the greatest impact is breast.

Beginning with the 2018 diagnosis year, the Collaborative Stage Data Collection System was decommissioned by the Canadian Council of Cancer Registries and use of the eighth edition of the American Joint Committee on Cancer’s tumour–node–metastases staging system (TNM 8th edition) was mandated.

• TNM 8th edition has stricter requirements than the Collaborative Stage Data Collection System for key data elements when mapping to an overall stage group. Due to these stricter requirements, in 2018 there is an increase in unknown stage group cancers and a shift in stage distribution for certain cancer types compared with previous years. As a result, it is recommended that comparisons be avoided between pre- and post-2018 stage data.
• The introduction of TNM 8th edition has resulted in an increase in unknown stage group cancers. This increase is primarily due to the lack of the computer algorithm that was part of the Collaborative Stage Data Collection System, which derived a “combined best stage” using whatever clinical and pathological data elements the cancer registrar was able to collect from the patient record.

Contributing facilities to activity-level reporting data used for population-level staging, Ontario

Regional cancer centres

• Cancer Centre of Southeastern Ontario
• Carlo Fidani Peel Regional Cancer Centre
• Grand River Regional Cancer Centre
• Juravinski Cancer Centre
• London Regional Cancer Program
• Northeast Cancer Centre
• Odette Cancer Centre
• Princess Margaret Cancer Centre
• R.S. McLaughin Durham Regional Cancer Centre
• Regional Cancer Care Northwest
• Simcoe Muskoka Regional Cancer Centre
• Stronach Regional Cancer Centre
• The Ottawa Hospital Cancer Program
• Windsor Regional Cancer Centre

Hospitals

• Alexandra and Marine General Hospital
• Alexandra Hospital
• Bluewater Health Sarnia General
• Brant Community Healthcare System, Brantford
• Brockville General Hospital
• Cambridge Memorial Hospital
• Chatham Kent Health Alliance, Chatham
• Collingwood General and Marine Hospital
• Cornwall Community Hospital
• Four Counties Health Services Corp
• Georgian Bay General Hospital, Midland
• Grand River Hospital Corp, Waterloo
• Grey Bruce Health Services, Owen Sound
• Guelph General Hospital
• Halton Healthcare Services Corp Oakville
• Hamilton Health Sciences Corporation Juravinski
• Hawkesbury and District General Hospital
• Headwaters Health Care Centre
• Health Sciences North, Laurentian Site
• Hôpital Montfort
• Humber River Hospital, Wilson Site
• Joseph Brant Hospital
• Kemptville District Hospital
• Kingston Health Sciences Centre (HDH)
• Kingston Health Sciences Centre, Kingston General
• Kirkland and District Hospital
• Lake of the Woods District Hospital
• Lakeridge Health Oshawa
• Lennox and Addington County General Hospital
• Listowel Memorial Hospital
• London Health Sciences Centre Victoria Hospital
• Mackenzie Health Richmond Hill Hospital
• Markham Stouffville Hospital
• Muskoka Algonquin Healthcare, Bracebridge
• Muskoka Algonquin Healthcare, Huntsville
• Niagara Health System, St Catharines General
• Norfolk General Hospital
• North Bay Regional Health Centre
• North York General Hospital
• Northumberland Hills Hospital
• Orillia Soldiers' Memorial Hospital
• Ottawa Hospital (The)
• Pembroke Regional Hospital Inc.
• Perth & Smiths Falls District Smiths Falls
• Peterborough Regional Health Centre
• Queensway Carleton Hospital
• Quinte Healthcare Corporation Belleville
• Renfrew Victoria Hospital
• Riverside Health Care Facility
• Ross Memorial Hospital
• Royal Victoria Regional Health Centre
• Sault Area Hospital, Sault Ste Marie
• Scarborough Health Network, Centenary
• Scarborough Health Network, Scarborough General Site
• Sinai Health System Mount Sinai Site
• South Bruce Grey Health Centre Kincardine
• Southlake Regional Health Centre
• St. Joseph's General Hospital
• St. Joseph's Health Care London
• St. Joseph's Health Care System Hamilton
• St. Mary's General Hospital
• St. Mary's Memorial Hospital
• St. Thomas Elgin General Hospital
• Stevenson Memorial Hospital Alliston
• Stratford General Hospital
• Strathroy Middlesex General Hospital
• Sunnybrook Health Sciences Centre
• Temiskaming Hospital
• Thunder Bay Regional Health Sciences Centre
• Tillsonburg District Memorial Hospital
• Timmins & District General Hospital
• Toronto East Health Network, Michael Garron Hospital
• Trillium Health Partners Credit Valley
• Trillium Health Partners Mississauga
• Trillium Health Partners Queensway Health
• Unity Health Toronto St. Joseph's
• Unity Health Toronto St. Michael's
• University Health Network Princess Margaret
• West Parry Sound Health Centre
• William Osler Health System
• Winchester District Memorial Hospital
• Windsor Regional Hospital, Metropolitan
• Windsor Regional Hospital, Ouellette Campus
• Women's College Hospital
• Woodstock General Hospital

Coding Rules for Multiple Primary Cancers

Different rules exist to determine whether a cancer is a new primary cancer or an extension of a previous cancer. Following a recent rebuild and similar to other North American cancer registries, the Ontario Cancer Registry adopted the Surveillance, Epidemiology and End Results Program's rules for counting multiple primaries and assigning histology. ^[9]

To identify multiple primary cancers, the Surveillance, Epidemiology and End Results counting rules take into account histology, site, laterality and time since the initial diagnosis. The Surveillance, Epidemiology and End Results rules are more liberal than the rules previously used in the Ontario Cancer Registry for counting multiple primaries in their definition of a new primary case.

The Surveillance, Epidemiology and End Results rules for multiple primary cancers have been applied to cases in the Ontario Cancer Registry diagnosed on or after January 1, 2010.

Cases from the years before the Surveillance, Epidemiology and End Results rules adoption (i.e., 1964 to 2009) have been imported into the new Ontario Cancer Registry from the Ontario Cancer Registry Information System for continued analytic use. The Ontario Cancer Registry Information System applied a modified version of the International Agency for Research on Cancer/International Association of Cancer Registries (IARC/IACR) rules [10], which are more conservative than the Surveillance, Epidemiology and End Results rules. Under the IARC/IACR rules, only 1 tumour is registered for an organ, irrespective of time, unless there are histological differences. ln this report, data were converted using the IARC/IACR rules when:

• trend analyses span both the Ontario Cancer Registry (2010 onward) and Ontario Cancer Registry Information System (1983 to 2009) eras
• comparisons are made between data from the 2 registry systems

When data are presented only from 2010 onward, the Surveillance, Epidemiology and End Results Program rules were applied.

Given that the Surveillance, Epidemiology and End Results rules are more liberal than the IARC/IACR rules, applying the Surveillance, Epidemiology and End Results Program rules results in an increase in the number of cases included in incidence counts. This is simply a result of using a different methodology and does not reflect an actual increase in the number of people diagnosed with cancer. In 2018, 4.2% of new cases were considered multiple primaries in Ontario.

Childhood Cancer Data

The Pediatric Oncology Group of Ontario Networked Information System (POGONIS), maintained by the Pediatric Oncology Group of Ontario and funded by the Ontario Ministry of Health, is the data source for the 0 to 14 age group. POGONIS is a reliable, validated data source used to estimate incidence, inform policy and planning, and provide essential data for research on childhood cancer cases in Ontario.

POGONIS, like the Ontario Cancer Registry, is a dynamic database, with data continuously being entered into it. The childhood cancer data used in this report were extracted from POGONIS in April 2021.

POGONIS is a population-based registry and database that captures detailed demographic, diagnostic, treatment and outcome information starting in 1985 on all children and adolescents diagnosed or treated with cancer in a specialized childhood cancer program in Ontario. Standardized POGONIS data are actively collected by dedicated data managers or clinical research associates at each of the 5 tertiary centres with specialized childhood cancer programs across Ontario. The information comes from comprehensive hospital chart review, internal hospital information systems and direct connections with patient healthcare teams. Death information in POGONIS is validated and supplemented via annual record linkage to the Ontario Cancer Registry and the Ontario Registrar General Death File under a data sharing agreement with Ontario Health (Cancer Care Ontario) to systematically capture deaths in the entire cohort.

The Pediatric Oncology Group of Ontario is also designated as a prescribed entity under the Personal Health Information Protection Act. The Pediatric Oncology Group of Ontario has created and operationalized detailed policies and procedures that govern all aspects of the collection, use and disclosure of personal health information.

Classification

The POGONIS database classifies childhood cancer according to the International Classification of Childhood Cancer, third edition (ICCC-3).^[11] This classification divides childhood cancer into 12 main diagnostic groups and 47 sub-groups for additional refinement.

The classification of each case applied in this analysis is true to the timing of the diagnosis and the associated International Classification of Diseases for Oncology (ICD-O) morphology code for that period. Because the ICCC-3 (published in 2005) does not incorporate coding changes made in the updated version of the ICD-O-3 system (ICD-O-3.1, published in 2013), the Pediatric Oncology Group of Ontario has incorporated changes to the ICD-O-3.1 codes into an updated ICCC classification based on Ontario clinical and epidemiological expertise. Details of the differences in coding between POGONIS and the ICCC-3 are available in the Pediatric Oncology Group of Ontario Surveillance Report.

Population data

lncluded in incidence, mortality and survival analyses:

• children diagnosed from ages 0 to 14 and residents of Ontario who were treated in a specialized childhood cancer program in Ontario with a diagnosis included in the in Pediatric Oncology Group of Ontario updated ICCC-3 classification system

Excluded from incidence, mortality and survival analyses:

• children who were not residents of Ontario, but who were diagnosed or treated in a specialized childhood cancer program in Ontario
• cases not diagnosed and fully treated in a specialized childhood cancer program in Ontario

The population used in this report for age standardization for childhood cancers is the 2011 Canadian Standard population (Table A.4).

Coding rules for multiple primary cancers

Childhood cancer incidence counts and rates are based on all cases of cancer diagnosed in children, ages 0 to 14 at time of diagnosis for the 1986 to 2020 period, who were diagnosed in a specialized childhood cancer program in Ontario and registered in POGONIS. Every occurrence of childhood cancer is considered an incident (or new) case. Following the International Agency for Research on Cancer rules for primary cancers, the Pediatric Oncology Group of Ontario registers or counts neoplasms of different morphology as multiple cancers (even if they are diagnosed simultaneously in the same site).^[10]

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