Cancer in Young People in Canada Data Tool

Data sources

The survival and relapse risk graphs and tables were created using data from the Cancer in Young People in Canada program (CYP-C).

Cancer in Young People in Canada (CYP-C)

CYP-C aims to include all children diagnosed under the age of 15 years who were treated at a pediatric oncology centre in Canada with a diagnosis listed in the International Classification of Childhood Cancer, 3rd Edition (ICCC-3). Only cases diagnosed between 2001 and 2020 are included. Each case registered in CYP-C is followed up to five years from the date of diagnosis. Cases were followed up to December 31, 2021.

There are two broad methods of data collection:

• In Ontario, the Pediatric Oncology Group of Ontario (POGO) has maintained a population-based registry of incident cancer cases since 1985, diagnosed or treated in one of the five pediatric oncology centres in the province. POGO shares this information with the Public Health Agency of Canada through a data sharing agreement.
• In all other Canadian jurisdictions, data are abstracted directly from patient medical charts by clinical research associates and entered into a secure electronic data entry and management tool (known as eCYP). Data are then collated at the Public Health Agency of Canada in Ottawa, Ontario.

Research ethics boards at the Public Health Agency of Canada and all pediatric oncology centres outside of Ontario participating in direct data collection have permitted CYP-C to collect detailed data on every eligible child, creating a population-based surveillance system.

Data was extracted from CYP-C on November 7, 2022, and from POGONIS on June 20, 2022.

Methodology

Overview

Children and youth (under 15 years old) diagnosed with cancer, between 2001 and 2020, are included in the survival data tool. Cases with the same date of diagnosis and death were assigned one day of survival and are included in the survival estimates. Only the first malignant primary diagnosis for each patient is included.

Selections

Sex: The sex of the child or youth.

Age: The age group of the child or youth at the time of their diagnosis: <1 year, 1 to 4 years, 5 to 9 years, 10 to 14 years, and All ages (<15 years).

Period of diagnosis: The 5-year period of a child or youth’s cancer diagnosis: 2001–2005, 2006–2010, 2011–2015, and 2016–2020.

Cancer: The cancer diagnosis of the child or youth. See Childhood cancer classification below for more information.

Risk groups for all ICCC diagnosis groups except for leukemia:

Extent of disease: The extent of disease for solid tumours indicates the presence of metastatic disease or no metastatic disease.

Risk groups for lymphoid leukemias (ALL):

Phenotype: The phenotype identifies the subtype of ALL. Leukemia subtypes (or immunophenotypes) are typically based on the type of lymphocyte (most often B cell or T cell) the leukemia cells come from, and how mature the cells are. The three phenotypes are:

• Precursor B-cell
• T-cell
• Mature B-cell (also known as Burkitt's Leukemia)

Central nervous system (CNS) involvement: CNS involvement indicates that leukemia has spread to the brain or spinal cord (at diagnosis). It is defined as the number of white blood cells (WBCs) in the cerebrospinal fluid (CSF).

• CNS 1 indicates that no blasts (immature white blood cells) are in the CSF.
• CNS 2 indicates that the WBC count is less than 5/μL, with blasts in the CSF.
• CNS 3 indicates that the WBC count is 5/μL or greater, with blasts in the CSF (or there are signs that leukemia has spread to the CNS).

Testicular involvement: Testicular involvement indicates that, at diagnosis, a biopsy or clinical evidence indicated evidence of testicular involvement.

NCI risk: The National Cancer Institute (NCI) describes risk groups in childhood ALL:

• NCI Low (standard) risk includes children aged 1 to younger than 10 years, with a WBC less than 50,000/µL at the time of diagnosis.
• NCI High (or very high) risk includes all other children.

The NCI risk group selection is available for precursor B-cell ALL, for diagnoses in 2007-2010, 2011-2015, and 2016-2020. To view data for NCI Low Risk and NCI High Risk for diagnoses in 2007-2010 select "2006-2010".

Risk groups for acute myeloid leukemias (AML):

French-American-British (FAB) classification: The FAB classification identifies the subtype of AML. Subtype “M3” refers to acute promyelocytic leukemia. All other subtypes are grouped together as “M0-M7 except M3”.

Measures

Observed survival

Overall survival: The observed overall survival proportion was calculated as the time from diagnosis until death, end of follow-up, or up to the end of the study (December 31, 2021).

Event-free survival: The observed event-free survival proportion was calculated as the time from diagnosis until first event (relapse, second malignancy, or death, whichever occurred first), end of follow-up, or up to the end of the study (December 31, 2021).

The observed survival functions presented in the figures were estimated by the Kaplan-Meier method, with all event times rounded to the nearest month. Confidence bands are equal precision (EP) bands.

The one-, three-, and five-year observed survival (OS) proportions are presented in the tables. Results for individual ICCC diagnostic groups were derived using the cohort method or the period method, based on an algorithm developed by Dickman.^{Footnote 1}

• For cases diagnosed in 2001–2005, 2006–2010, or 2011–2015, survival proportions were estimated using the cohort method (actual rates). These cases have completed a five-year follow up.
• For cases diagnosed in 2016–2020, survival proportions were estimated using the period method. These cases have not completed a five-year follow-up.

Results for all cancers combined were calculated as a weighted average of the estimates from individual cancer types. The weights employed were based on the distribution of the 12 main ICCC groups diagnosed in Canada in 2016–2020.

Cumulative incidence of relapse

Cumulative incidence of relapse: The cumulative incidence of relapse was calculated with death or development of second cancer (before experiencing a relapse) considered as competing risks.

Childhood cancer classification

Cancer and tumour types were defined using the International Classification of Childhood Cancer (ICCC). The ICCC is a diagnostic classification system for childhood cancer based on tumour morphology and primary site, with a greater emphasis on morphology as compared to the classification of cancers for adults.

The ICCC is coded using ICD-O-3, based on the definitions presented in Steliarova-Foucher et al. (2017), known as ICCC, Third Edition based on ICD-O-3/IARC 2017.^{Footnote 2}

Multiple primaries were defined according to the International Agency for Research on Cancer’s (IARC) rules.

Suppression

Categories with less than 30 cases have been excluded.

References