Adult Cancer Surveillance

Adult Cancer Surveillance

Objectives:

• Monitor and analyze information on cancer incidence, mortality, survival, time trends, geographic patterns and high risk populations: an estimated 129,300 new cases of cancer will be diagnosed and an estimated 63,400 deaths will occur in 1999.
• Project future cancer burden:  the number of cases of cancer is expected to increase by 70% by the year 2010 as a result of the increased size and age distribution of the population.
• Evaluate the economic impact of cancer:  the direct costs of cancer were estimated at $3.2 billion and the indirect costs were estimated at $9.8 billion in 1993.

Preparation of Canadian Cancer Statistics 1999

As of the 1999 edition, the Cancer Bureau provided all estimates and tabulations included in Canadian Cancer Statistics, an annual monograph published by the National Cancer Institute of Canada (NCIC) in collaboration with the Canadian Cancer Society, Statistics Canada, the Canadian Council of Cancer Registries, and university-based cancer researchers. The publication provides detailed information on the incidence and mortality of the most common types of cancer, by age, sex, time period and province. The 1999 edition presents factors contributing to the population burden of cancer incidence and mortality and a description of a vision for a new national cancer surveillance system for Canada.

On the basis of estimates for 1999, breast cancer in women and prostate cancer in men continue to be the most frequently diagnosed cancers; lung cancer remains the leading cause of cancer deaths in both sexes (see table below).

Targeted Case Surveillance

Descriptive statistics about the Canadian population and subpopulations are prepared from cancer surveillance data. Examples include the following:

• A report on testicular cancer trends by histological group has been prepared.
• Lung cancer trends among young Canadians, specifically  incidence and mortality rates, are being examined. For Canadians aged 25-44, both incidence and mortality rates are now higher among females than males. This will have an impact on the future burden of cancer in Canada.
• Unequal cancer risks between immigrant and Canadian populations are being assessed, their determinants analyzed and their impact on the Canadian health care system measured.  The change in disease risk by length of stay in Canada will also be studied.
• Rates of human papilloma virus (HPV) and cervical cancer among the Aboriginal population of Baffin Island are being examined for potential associations.
• Cancer incidence and potential risk factor data for the Northwest Territories are being mapped in collaboration with the Environmental Health Directorate of Health Canada and the Government of the Northwest Territories.
• Cancers affecting women (e.g. ovarian, cervical) and those cancers for which the incidence and mortality patterns vary according to sex (e.g. pancreas, lung) are being examined. Factors responsible for differences between male and female mortality and survival trends are being identified.

Breast Cancer Initiative

Several projects are in progress to examine specific issues related to breast cancer:

• One project uses National Enhanced Cancer Surveillance (NECS) risk factor data to examine the association between exposure to environmental tobacco smoke (passive smoking) and breast cancer. The risks have been calculated, allowing for the effect of factors such as diet and occupation, and the results have been submitted for publication.
• In collaboration with the Manitoba Cancer Treatment and Research Foundation, second primary breast cancers are being investigated using data from hospital charts and registrations.
• Two-year survival rates for breast cancer have been examined by stage of cancer at diagnosis using data obtained from the Ottawa Regional Cancer Centre; the results have been published. Five-year survival data are now being collected.

Breast Implant Epidemiology Study

Data collection is now complete for a population-based cohort of approximately 31,000 breast implant patients and 16,000 matched controls in Ontario and Quebec. Phase One focuses on cancer risk. The study will compare the cohort with the control group and the general population of Canada through cancer and death registries. The cohort developed in Phase One will be available for Phase Two studies to assess health outcomes other than cancer.

Impact of Social Status on the Development of Cancer in Canada

This study will provide general information to help understand the inequality of cancer development in the Canadian population and its subpopulations. It will also estimate the population attributable risk fraction for physical and environmental risk factors in Canada. Using the NECS database, the impact of various measures (e.g. family income, marital status, education, smoking, residence, occupation) on selected cancer sites (breast, lung, stomach, colon, rectum, pancreas, bladder, prostate, etc.) will be assessed.

Support for Canadian Coalition on Cancer Surveillance

Cancer registration, staging and treatment data are obtained from the Canadian Cancer Registry partners and cancer centres to develop a standardized core data set. Quality assurance standards are being developed and implemented to support CCOCS goals.

Population-Based Cancer Survival Assessment and Applications

This collaborative project will develop standards and methods for Canada-wide data collection and interpretation used in survival analysis. The data will be used to investigate the effects of major cancer determinants, prognostic factors and treatment modalities on cancer survival in Canada. A workshop in June 1997 identified information needs and recommended directions to establish mechanisms that would generate this information. An overview of uses, barriers and priorities was published in Chronic Diseases in Canada in 1998. Initial work on stage-specific analysis is now under way, and a paper has been published on stage-specific survival for breast, lung and colorectal cancers.

Predicted Impact of Cancer

Initiated by the NCIC and the LCDC, the Canadian Cancer Projections System is being developed to standardize methods for estimating the future burden of cancer. Provincial cancer registries and LCDC will use these methods to achieve long-term projections across Canada. An age-sex specific smoking prevalence data set by 20-year age group has been created from available survey data (1975 to 1995) at the national and provincial levels.

Information generated from this project will assist the provinces and Health Canada in making evidence-based decisions on priority setting, resource allocation and long-term planning.

The figure that follows, which appeared as part of a special topic in Canadian Cancer Statistics 1999, depicts how changes in three factors - population growth, age-structure and the annual cancer rate over time - contribute to the annual number of cancer cases/deaths. The method developed estimates the proportion attributed to each of these factors using 1971 as a baseline. The lowest series (as indicated by the dotted line) plots the observed 1971 counts. The series above this was created by holding the population to that of 1971 and estimating the expected number of cases based on annual rates of the year in question. The next series is an estimate of what the cancer counts would have been if the age distribution of 1971 was held constant through time. In other words, the total population of each year, although changing, is forced to have the same percentages in each age group as were present in 1971. This redistribution of the population into 1971 percentages is multiplied by the annual age- and sex-specific rates and then summed to produce an estimate for that year.

Figure 2 Total Number of New Cases or Deaths, Showing the Contribution of Change in Cancer Risk, Population Growth, and Change in Population Age-Structure (1971 reference), All Cancers, All Ages, Canada, 1971-1999

Note: Incidence figures exclude non-melanoma skin cancer (ICD-9 173). Magnitude of area represents the number of cases/deaths due to each change. Source: Cancer Bureau, LCDC, Health Canada

The final series is a plot of the annual observed or projected counts.  Differences between the four series provide the respective contributions of the three factors mentioned above.  Changes in age structure accounted for the largest proportion.  Males and females showed similar patterns. For a complete explanation of this figure, please refer to National Cancer Institute of Canada: Canadian Cancer Statistics 1999, Toronto, Canada, 1999:53-5.

Women's Cancer Information Monograph

This comprehensive monograph will provide a wealth of information to Canadian women on all aspects of cancer throughout its life cycle, prevention to treatment. Several chapters have already been written and are being edited to provide easy to understand information and comprehensive recommendations. The targeted release date is April 2000.