Cancer incidence in Canada: trends and projections (1983-2032)

Abstract

In this monograph, we present historical and projected cancer incidence frequencies and rates for Canada, excluding non-melanoma skin cancers (i.e. basal and squamous carcinomas), in 1983 to 2032. The information is intended to help in planning strategy and allocating resources and infrastructure for future cancer control and health care. Projected changes in cancer incidence rates: From 2003-2007 to 2028-2032, the agestandardized incidence rates (ASIRs) for all cancers combined are predicted to decrease in Canadian males by 5%, from 464.8 to 443.2 per 100 000 population, and increase in Canadian females by 4%, from 358.3 to 371.0 per 100 000. The overall decrease in cancer rates in males will be driven by the decrease in lung cancer rates in men aged 65Endnote * or older and in prostate cancer rates in men aged 75 or older. The overall increase in cancer rates in females reflects the predicted rise in lung cancer rates in women aged 65 or older. The increase also represents the expected increase in cancers of the uterus, thyroid, breast (in females under 45), leukemia, pancreas, kidney and melanoma. The largest changes in ASIRs projected over the 25-year forecasting horizon are increases in thyroid cancer (55% in males and 65% in females) and liver cancer in males (43%) and decreases in larynx cancer (47% in males and 59% in females), lung cancer in males (34%) and stomach cancer (30% in males and 24% in females). The incidence rate of lung cancer in females is projected to continue to rise by 2% from 2003-2007 to 2008-2012 and then start to decrease in the last 20 projection years, by 18%. Breast cancer incidence is expected to change the least (an increase of less than 1%) of all cancers in females. The predicted changes in the rates for colorectal cancer are below the medians in all cancers, with a decrease of 6% for both males and females during the entire projection period. The rates for prostate cancer are projected to be stable, based on an assumption of future stabilization in the prevalence of screening. New cancer cases to rise: The annual number of new cancer cases is predicted to increase by 84% in Canadian males, from 80 800 in 2003-2007 to 148 400 in 2028-2032, and by 74% in Canadian females, from 74 200 to 128 800. Drivers of the changes in cancer cases: The primary reason for the increase in the number of all newly diagnosed cancer cases will be the aging of the Canadian population and, to a lesser extent, the increase in population size. Changes in the risk of cancer will constitute a relatively small component of the projected increase in new cases. Preventive interventions can have a strong influence on future incidence rates for individual cancer types. Most common cancers: The most common new cancers in males--prostate, colorectal, lung and bladder cancers, and non-Hodgkin lymphoma--are projected to remain the same from 2003-2007 to 2028-2032, but colorectal cancer is predicted to outrank lung cancer as the second most frequently diagnosed cancer by 2028-2032. For females, breast, lung, colorectal and uterine cancers figure as the top 4 most common incident cancers in both periods. However, thyroid cancer will overtake non-Hodgkin lymphoma as the fifth most common cancer by 2028-2032. Incidence by geographical region: There is an east-west gradient in incidence across Canada. The highest incidence rates for most cancers are projected to be in eastern Canada (Atlantic region [New Brunswick, Prince Edward Island, Nova Scotia, and Newfoundland and Labrador], Quebec or Ontario) for both males and females. While British Columbia is projected to continue to have the lowest incidence rates for the majority of cancers in both sexes, this province will also continue to experience the highest rates for esophageal cancer in females, liver cancer in both sexes and testis cancer. The Atlantic region is projected to have the lowest incidence rates for cancers of the breast, uterus and ovary in females, and for liver cancer and leukemia in both sexes. In contrast, this region is projected to experience elevated incidence rates in males for about half the cancers studied. The incidence rates for all cancers combined are projected to continue to be highest for males in the Atlantic region and for females in Quebec in 15 years but in Ontario thereafter, and lowest in British Columbia. The inter-regional differences are larger in males than in females, possibly due to variations in prostate-specific antigen (PSA) testing (for prostate cancer) and risk factors. In both males and females, colorectal cancer incidence rates will remain highest in the Atlantic region and lowest in British Columbia. Lung cancer incidence rates are projected to be highest in Quebec and lowest in Ontario and British Columbia for both sexes. The similar regional rates of breast cancer in females are expected to persist. The significantly lowest rates of prostate cancer in Quebec are projected to continue, as are the elevated rates in the Atlantic region. Incidence by sex and age: Cancer is more common in males than in females except in those aged under 55. The overall cancer incidence rate in men aged 65 or older has been falling and will continue to do so. The decrease in lung cancer rates in men aged 65 or older from decreased tobacco use and the decrease in prostate cancer rates in men aged 75 or older have contributed to the overall decrease in this age range. In women aged 65 or older, the relatively stable rate is primarily the result of an increase in lung cancer incidence offset by decreases in incidence for the other cancer sites. This stable trend is projected to continue. Targeted cancer prevention efforts and specific needs for health care services can be expected to vary at different points in the age continuum for males and females. Smoking-related cancers: Between 2003-2007 and 2028-2032, substantial risk reductions are projected for major common tobacco-related cancers in Canada, even with relatively lower reductions or delayed downturn trends in females. The differences between males and females in the predicted incidence trends of these cancers mirror the historical pattern of reductions in smoking prevalence that took place in males 20 years earlier than in females. Given the lag of 20 years or more between the reduction in smoking and subsequent decrease in cancer incidence, the incidence rates in females will likely begin to drop more noticeably over the longer term. By comparison, the risk of cancer incidence is forecast to increase for non-tobacco-related cancers. Cancers associated with excess weight and physical inactivity: Over the 25-year projection period, the incidence rates for cancers associated with excess weight and physical inactivity are estimated to increase by 0.6% to 16% for cancers of the uterus, kidney, pancreas, female breast and male esophagus, in descending order. Incidence rates are expected to decrease by 2% to 6% for colorectal and female esophageal cancer. Increased obesity prevalence in Canada may contribute to the increased incidence trends. Most common infection-associated cancers: From 2003-2007 to 2028-2032, the incidence rates of liver cancer are expected to escalate almost 3 times faster in males than in females (43% vs. 15%), while the rate of stomach and cervical cancer will continue to decrease by 20% to 30%. The ongoing increasing trend of liver cancer incidence is possibly linked to the historical increase and continued high incidence in hepatitis C virus (HCV) infection, the aging of the previously infected population, and increasing immigration from areas where risk factors such as hepatitis B virus (HBV) are prevalent. The persisting decrease in incidence of stomach cancer may be explained by improved healthy behaviours, such as decreased smoking and changes in diet, and increased recognition and treatment of Helicobacter pylori infection. The continuing downward trend in the rates of cervical cancer is mainly attributable to general population screening with the Papanicolaou (Pap) test and successful treatment of screening-detected premalignant lesions. The immunization of school-aged children with the vaccine for human papilloma virus (HPV) is anticipated to further reduce the incidence of cervical cancer. Implications for cancer control strategies: The projected aging and growth of the population are expected to lead to a progressive and significant increase in the total number of new cancer cases in Canada over the next 25 years. Consequently, this report indicates the need to continue to strengthen cancer control strategies and leverage resources to meet future health care requirements and reduce the burden of cancer in Canada. Although incidence rates are projected to decrease for many cancers, the rates for some cancers, for example, thyroid, liver, uterus, pancreas, kidney and leukemia, are estimated to increase. Additional etiological research is needed to better understand risk factors and guide prevention efforts. This monograph underscores the importance of cancer prevention by curbing smoking; promoting healthy eating, physical activity and weight management; enhancing uptake of cancer screening; and increasing coverage of HPV vaccination. The implication of future changes in our demographic profiles and cancer trends should be addressed from the full spectrum of cancer control, including research and surveillance, prevention and early detection, treatment, and psychosocial, palliative and medical care.

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