The Data

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Cancer incidence data are from the July 2010 version of the Canadian Cancer Registry (CCR), a dynamic, person-oriented, population-based database maintained by Statistics Canada.  The CCR contains information on cases diagnosed from 1992 onward, compiled from reports from every provincial/territorial cancer registry. 

A file containing records of invasive cancer cases and in situ bladder cancer cases (the latter are reported for each province/territory except Ontario) was created using the multiple primary coding rules of the International Agency for Research on Cancer.⁸  Cases were classified based on the International Classification of Diseases for Oncology, Third Edition⁹ and grouped using Surveillance, Epidemiology, and End Results Program grouping definitions, with mesothelioma and Kaposi's sarcoma as separate groups.¹⁰ 

Mortality through December 31, 2006 was determined by record linkage to the Canadian Vital Statistics Death Database (excluding deaths registered in the province of Quebec), and from information reported by provincial/territorial cancer registries.  For deaths reported by a provincial registry but not confirmed by record linkage, the date of death was assumed to be that submitted by the reporting registry.

Analyses were based on all primary cancers—an approach that is becoming standard practice.^11-13  Data from the province of Quebec were excluded from the analysis primarily because of issues associated with correctly ascertaining the vital status of cases.  Records were also excluded if:  age at diagnosis was younger than 15 or older than 99; diagnosis was established through autopsy only or death certificate only; or the year of birth or death was unknown. 

In the context of cancer, conditional survival is the probability of living an additional number of years (y) given that the person has already survived a fixed number of years (x) since diagnosis.  The measure can be obtained by dividing the cumulative survival at x + y years by the cumulative survival at x years.  Conditional five-year relative survival expresses the likelihood of surviving five years into the future at various points since diagnosis, relative to the expected survival of similar people in the general population.¹⁴

Relative survival was estimated as the ratio of the observed survival for people diagnosed with cancer to the survival expected for the general population with the same sex, age, province/territory at time of diagnosis and time period.  When a relative survival ratio (RSR) reaches 100%, survival for those diagnosed with cancer is similar to that of an otherwise comparable group in the general population.  RSRs were derived using the period method,^15,16 which provides more timely estimates of cancer survival.^17-20  When survival is generally improving, a period estimate tends to be a conservative prediction of the survival that is eventually observed.^17-20

Survival analyses were based on a publicly available algorithm²¹  to which minor adaptations were made.  Expected survival proportions were derived from sex- and period-specific complete provincial life tables using the Ederer II approach.²²  Further detail on the survival methodology is provided elsewhere.²³  For descriptive purposes, cancers were initially grouped according to the five-year survival prognosis at diagnosis:  good (80% or more), fair (50% to 79%), and poor (less than 50%).