Introduction

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Canada has a long record of data development to support cancer surveillance and control. The Canadian Cancer Registry (CCR), established in 1992, represents a collaborative undertaking between Statistics Canada and the thirteen provincial and territorial cancer registries to create a single database to report annually on cancer incidence and survival at the national and jurisdictional levels.¹ Data from the CCR are used for descriptive and analytic epidemiological studies to identify cancer risk factors; to plan, monitor and evaluate a broad range of cancer control programs (for example, screening); and to conduct research in health services and economics.²

While gains have been made in the production of high-quality, standardized, and therefore comparable data, the CCR lacks information about cancer treatment. This is partially because of the lack of national standards for the collection of treatment data by cancer registries. About half of registries collect some form of treatment data, but the treatment types that are recorded, their sources, and standards used for collection vary considerably across jurisdictions.

The Canadian Council of Cancer Registries (CCCR) identified the need to capture treatment data at the national level as a key strategic priority for 2013/2014.³ The addition of treatment information would enhance the CCR’s analytical capacity for researchers and epidemiologists. Furthermore, stakeholders at the provincial, territorial and national levels are interested in treatment data with respect to outcomes, wait times, surveillance and system performance monitoring. As a first step, the CCCR established the Treatment Working Group to define a minimum dataset for the CCR that would guide the collection of treatment information at the national level.⁴ The Treatment Working Group was mandated to assess the feasibility of various data collection approaches, including record linkage to address treatment data gaps.

Record linkage is commonly used to fill information gaps and “add value” to existing data sources. For example, linkages between survey and administrative data have enhanced the capacity to report on health outcomes such as hospitalizations, mortality of subpopulations such as immigrants, low-income groups and the homeless,^5,6,7,8,9 and have improved understanding of risk factors to health across time.¹⁰ Previous record linkages between provincial cancer registries and other health administrative data have provided new information about cancer treatment,^11,12,13 patient experiences with health care^14,15 and subsequent health risks related to initial cancer events.¹⁶

This study examines the feasibility of using record linkage to add treatment information to the 2005-to-2008 CCR for selected cancers―breast, colorectal and prostate. The objectives are to assess the quality of the linkage processes and the validity of using linked data to estimate cancer treatment rates at the provincial level. A project to link the CCR to the Discharge Abstract Database (DAD) and the National Ambulatory Care Reporting System (NACRS) for four provinces (Ontario, Manitoba, Nova Scotia and Prince Edward Island) was jointly proposed by Statistics Canada, the CCCR and the Canadian Institute for Health Information (CIHI). The linkage was approved by the Statistics Canada Policy Committee (June, 2012).¹⁷ Use of the linked data is governed by the Directive on Record Linkage.¹⁸