This indicator examines the age-standardized incidence rates for non-metastatic prostate cancer by stage at diagnosis (I, II, III, IV). Only men aged 35 or older were included, as prostate cancer is extremely rare in men under age 35.
As of 2010, population-level stage data were available in nine of 10 Canadian provinces for the four most common cancers including prostate cancer. The availability of such data provides new opportunities: they can be used to support system-level surveillance of cancer trends, to more accurately measure system performance, and to evaluate the impact of differences in early detection and screening efforts across the country—in particular, how they affect patient outcomes.
What are the results?
In the 2010 diagnosis year, Stage II was the most common stage for prostate cancer in all provinces, with the exception of Prince Edward Island where the Stage I age-standardized incidence rate was highest.
The incidence of Stage I prostate cancer showed great variation across the country in the 2010 diagnosis year, ranging from 12.9 cases per 100,000 in British Columbia to 141.0 cases per 100,000 in Prince Edward Island.
The incidence of Stage II prostate cancer ranged from 75.8 cases per 100,000 in British Columbia to 164.7 cases per 100,000 in Newfoundland and Labrador.
The incidence of Stage IV prostate cancer was the least frequent in most provinces, ranging from 15.3 cases per 100,000 in British Columbia to 36.3 cases per 100,000 in Saskatchewan.
What do the results mean?
The interprovincial variation in the stage-specific incidence rates could reflect differences in the use of PSA testing across jurisdictions or staging data issues (see Data and measurement considerations). Those with a higher rate of PSA testing would be expected to have a higher incidence of early-stage prostate cancer. In order to reliably link stage-specific incidence patterns to differences in PSA testing rates across the country, we need reliable data on PSA testing rates for all provinces; these are not available.
Age-standardized incidence rate: crude incidence rates for prostate cancer were calculated for men aged 35 and older, standardized to the age structure of the 2011 Canadian population (aged = 35).
Stage-specific incidence rates measure the number of people per 100,000 diagnosed at each stage of disease for a specific type of cancer, at the time of diagnosis.
Assigning a case as stage unknown means that the pathological and/or clinical diagnosis was not complete or that the information available in patient charts was not sufficient to ascertain a stage. In the 2010 stage-specific incidence data used in this indicator, the cases deemed to be stage unknown was particularly high in British Columbia: 54.9 cases per 100,000 compared to a range of 1.4 to 16.3 per 100,000 in other provinces (this is at least partially due to a lack of available documentation providing PSA and Gleason score information for patients not referred to the BC Cancer Agency). The high rate of stage unknown can compromise the ability to compare provincial stage-specific incidence rates.
Blank stage means that the collaborative stage (CS)h algorithm was not run or resulted in an error.
The wide interprovincial variation in Stage I incidence rates could be explained by several factors. In the 7th edition of the American Joint Committee on Cancer (AJCC) Cancer Staging Manual, the addition of PSA and Gleason score has changed the way prostate cancer is staged, resulting in a greater number of Stage I cases. It is possible that some provinces may still be using the 6th edition of the AJCC Cancer Staging Manual and would, therefore, be expected to have a lower incidence of Stage I disease. Also, provinces with higher levels of PSA testing would be expected to have higher incidence of Stage I prostate cancer.
Data tables for this indicator (including confidence intervals), along with detailed calculation methodology contained in the full Technical Appendix, are available at systemperformance.ca.
Age-standardized incidence rates by stage
Definition: The incidence rate in each stage category that would have occurred if the age distribution in the population of interest was the same as that of the standard, where incidence rate is defined as the number of prostate cancer cases (men aged 35 and older) newly diagnosed during a specific time period, per 100,000 men.
Numerator: Of the denominator, the total number of prostate cancer cases (men aged = 35) newly diagnosed in 2010, by stage at diagnosis
Denominator: Total male population aged = 35 in 2010
Age standardization: Direct method using the 2011 Canadian Census population
Measurement timeframe: 2010 diagnosis year
Stratification variables: Province, stage (stage I, II, III, IV, Unknown, Blank)
Data sources: Statistics Canada, Canadian Cancer Registry; Provincial cancer agencies (BC and SK)
Provinces/territories with data available: BC, AB, SK, MB, ON, NB, NS, PE and NL
Stage data are not available for Quebec in 2010.
The “Unknown” category refers to cases with unknown staging.
The “Blank” category refers to cases when the Collaborative Staging (CS) algorithm was not run or resulted in error.
Population estimates provided by the Demography Division, Statistics Canada.
World Health Organization, International Classification of Diseases for Oncology, Third Edition (ICD-O-3) and the International Agency for Research on Cancer (IARC) rules for determining multiple primaries sites were used: prostate (ICD-O-3: C61.9).
American Joint Committee on Cancer 7 edition (AJCC 7) was used to classify cancer staging.
hCollaborative stage data collection system (CS) Using a specific computer-based methodology, trained coders—known as certified tumour registrars—are given access to all patient charts that contain clinical findings along with any pathological test results (i.e., analysis of tumour tissue or cells). The registrar receives and reviews the data, makes coding assessments and then inputs the data into the relevant fields. A computer generates the appropriate stage but also allows the inclusion of additional prognostic factors. This information is captured and stored in provincial cancer registries.