The Cancer in Young People in Canada surveillance system - HPCDP: Volume 35-4, June 2015

Volume 35 · Number 4 · June 2015

Introduction

Although childhood cancer remains the leading cause of disease-related deaths among children younger than 14 years of age, it is relatively rare.^{Endnote 1Endnote 2} Each year, an average of 910 children are diagnosed with cancer in Canada, and 139 children die of the disease.^{Endnote 3} Cancers in children differ biologically from those usually found in adults.^{Endnote 4Endnote 5} The majority of cancers in adults are carcinomas of the epithelial tissues that line organs such as the breast, lung, colon and prostate. In children, carcinomas are rare and childhood tumours are more likely to be embryonic or hematopoietic in origin.^{Endnote 5} Leukemias, lymphomas and central nervous system cancers represent the largest diagnostic groups.^{Endnote 5} Compared to cancers in adults, cancers in children have shorter latency periods and are generally more aggressive, invasive and advanced at diagnosis.^{Endnote 5}

Despite the high ranking of cancer as a cause of death in children, survival rates have improved substantially over the last two decades so that more children survive cancer than ever before.^{Endnote 6} However, over 60% of childhood cancer survivors face long-term physical and mental side-effects from the disease and its treatment, and nearly 30% have severe or life-threatening late effects.^{Endnote 7} Survivors of childhood cancer have an 11-fold increased risk of death, an increased risk of second cancers up to 30 years after treatment and a wide variety of chronic physical, psychosocial and cognitive problems.^{Endnote 8} The recognition of the unique nature of cancers in this age group and extensive long-term late effects has led many countries to establish specialized pediatric cancer surveillance and follow-up systems.^{Endnote 8Endnote 9Endnote 10Endnote 11Endnote 13}

In 2009, the Public Health Agency of Canada (PHAC) launched a pan-Canadian specialized childhood cancer surveillance system that actively follows children aged up to 14 years treated at one of the 17 pediatric oncology centres across the country (Table 1). The Cancer in Young People in Canada (CYP-C) program is a renewal of the federal government's Canadian Childhood Cancer Surveillance and Control program (CCCSCP). Established under the Brighter Futures Initiative in 1992, the program includes comprehensive data on a child's cancer diagnosis, treatments, outcomes and health care utilization.^{Endnote 12Endnote 13}

In this article, we describe the strengths and successes of CYP-C by highlighting rigour in data collection and quality control methodology as well as recent achievements and future directions.

Program objectives and data collection

CYP-C was designed to fill in gaps in knowledge about cancer control. The national program is one of the few pediatric cancer surveillance systems in the world that cover nearly all their target populations.^{Endnote 13} The objectives of the program are to

1. provide national and regional population-based childhood cancer data on incidence, mortality, survival and time trends;
2. describe patterns of incidence and survival of childhood cancer by diagnosis, stage, risk category and extent of disease;
3. assess short- and medium-term outcomes such as relapses, toxicities and complications related to treatment;
4. provide data on the timing, location and utilization of health care for evaluation and planning; and
5. function as a resource for generating hypotheses and research into pediatric cancer (see Table 2).

All children aged 0 to 14 years who are diagnosed with a new malignancy that is listed in the International Classification of Childhood Cancer, 3^rd Edition (ICCC-3)^{Endnote 4} in 2001 or later and who are residents of Canada for at least one month prior to their diagnosis are included in CYP-C. Langerhans cell and other histiocytosis are also included in CYP-C because of the histopathology of these conditions, even though they are not classified as malignant according to the International Classification of Diseases for Oncology, 3^rd Edition (ICD-O-3), on which the ICCC-3 is based.^{Endnote 4} Information is collected on each eligible case from diagnosis to 5 years postdiagnosis. In Ontario, the Pediatric Oncology Group of Ontario (POGO) collects similar data on childhood cancer cases treated in one of the five pediatric centres in the province.^{Endnote 14} Information is then shared with CYP-C through a data-sharing agreement. In all other jurisdictions, data are abstracted from patient charts and entered into an electronic data entry and management tool called E-CYP. Data are transmitted on a regular schedule over a secure connection to a national database maintained by PHAC. Direct identifiers such as names and health card numbers are not sent to the national database.

Research ethics approval has been given by participating hospitals and Health Canada to allow for data collection without individual consent for sites where direct data collection occurs.^{Endnote 15}

Current status

CYP-C has registered over 5850 cases and contains over 2900 cases with 5 full years of data diagnosed between January 1, 2001, and December 31, 2006 (Table 3). CYP-C data will be available for research once data from Ontario has been integrated into the surveillance system, which is expected to occur in the spring of 2015. This integration will be followed by the publication of a descriptive data report highlighting national childhood cancer statistics on incidence, mortality, treatment, and outcomes by age, sex, diagnosis, and geography. CYP-C data have already been used for local surveillance purposes and include a peerreviewed publication on morbidity and survival in First Nations children with cancer in Manitoba.^{Endnote 16}

Data quality

CYP-C aims to achieve complete and accurate case registration. Close collaboration between all clinical research associates and pediatric oncologists-hematologists at the participating centres and PHAC enable accurate and timely entry of case details. Built-in edit and logic checks ensure accuracy and validity, and include ranges and numeric entries for dates and the requirement for appropriate metrics for drug dosage fields. Data abstractors participate in an annual in-person training session to review case definitions and data entry procedures. They meet monthly by teleconference to discuss new challenges relating to data abstraction through a community of practice. During each data upload cycle, the database administrator conducts data quality control and validation procedures designed to identify missing information, logic and data consistency errors and duplicate entries. Reports summarizing results are submitted to the data abstractors for resolution. Periodic reabstraction audits are also performed to further ensure the accuracy of the data. Ten centres across the country have been audited and results show that key data items are abstracted correctly, with few transcription errors or omissions. Complex data items that require interpretation at the point of entry (for example, stage at diagnosis) appear to be most accurate in centres where data abstractors have access to oncologists and other experts.

The completeness of ascertainment is an integral component of the program and CYP-C is routinely compared to the Canadian Cancer Registry, the most complete source of data on new cancer cases in Canada.^{Endnote 17} A recent comparison showed that CYP-C includes approximately 90% of all children aged up to 14 years who have been diagnosed with cancer in Canada, with some regional variations in case ascertainment (Table 4). Investigations are underway for a study on the feasibility of linking the CYP-C data to provincial and/or national cancer and vital registries for data validation that will include the identification of missing cases, duplicates and death clearance.

Future prospects

CYP-C provides a population-based sampling frame for cancer control in the pediatric population through the systematic collection of data on risk factors, incidence, mortality and the cancer care continuum for each child diagnosed with a malignancy in Canada. The enhanced components of CYP-C allow for the examination of a wide array of issues that impact access, quality and equity in care, and ultimately, long-term health outcomes. It also forms a crucial basis for understanding the etiology and epidemiology of childhood cancers and helps to identify childhood cancer survivors most at risk of adverse health outcomes such as toxicities, relapses or second malignancies. The CYP-C program remains one of the most in-depth pediatric oncology surveillance systems in the world and will continue to expand until it approaches real-time data collection.^{Endnote 18}

Acknowledgements

The CYP-C surveillance system is fully funded by the Public Health Agency of Canada. We thank the C17 Council, participating pediatric oncology centres and members of the program's management and steering committees for their vision, guidance and support. We are grateful to patients and their families for providing information for CYP-C.

Contact: For current information on the CYP-C program, please contact cypc-ccjc@phac-aspc.gc.ca or visit the program website at www.c17.ca/index.php?cID=70.

References