Key findings

Download PowerPoint graphs for CSQI indicators

The number of people in Ontario living with cancer is increasing. Why? More people are getting cancer because the population is growing and aging, and survival rates have improved for almost all cancers. Screening and lifestyle continue to play an important role in cancer control.

How do incidence, mortality, survival and prevalence relate to one another?

• Incidence is a measure of cancer risk in the population.
• Mortality is determined by both incidence and prognosis .
• Prevalence is determined by both incidence and survival.

Incidence

What is incidence?

• Incidence is the rate at which new cases of cancer are diagnosed.
• Trends in the number of new cases are related both to trends in underlying cancer risk factors (such as smoking or physical inactivity), and to trends in population growth and aging (the risk of cancer increases with age).
• In 2011, approximately 69,900 new cancer cases are projected to be diagnosed in Ontario.
• Cancer risk in a population is related to many things in addition to age:
• Prevalence of important modifiable risk factors, such as tobacco use or obesity
• Uptake of HPV vaccines
• Screening patterns
• Social and physical characteristics, such as sexual behaviours, age at menopause and number of children
• Exposures to carcinogens such as asbestos in the workplace or environment
• Genetics
• Changes in these underlying factors over time result in changes to incidence rates.
• However, making direct connections between exposure to risk factors and cancer can be difficult, because cancer can develop quickly or slowly after exposure.
• Lung cancer rates, for example, typically take many years to reflect changes in provincial smoking rates.
• On the other hand, rapid uptake of screening can result in an apparent sudden rise in cancer diagnoses, as cancers are discovered earlier than they otherwise would have been.

Incidence is increasing for some cancers, decreasing for others (Figure 2)

• Incidence rates for prostate, uterine and ovarian cancer are projected to rise between 2008 and 2011.
• For prostate cancer, two periods of steeper increase coincide with increased use of the PSA test (which results in early diagnosis, before symptoms are present).
• Lung cancer incidence rates are decreasing for males and have now stabilized, following an earlier increase, for females.
• This likely reflects different past smoking trends between the sexes.
• Incidence rates for colorectal and cervical cancer are decreasing.
• Breast cancer incidence is no longer rising, after increasing up to the early 1990s.
• Stable rates from the 1990s onward likely reflect a combination of factors:
• A lack of increase in the proportion of women screened by mammography
• A decrease in the use of hormone replacement therapy after 2002
• The increasing tendency for a woman to delay childbirth to a later age

Focus on gynecological cancers (Figure 2)

• For the major gynecological cancers, incidence rates show differing patterns.
• Cancer of the body of the uterus has been increasing significantly since the mid-1990s and may be related to increasing obesity.
• Ovarian cancer incidence has increased since the 1980s.
• Ovarian cancer has been associated with hormone replacement therapy use and with having fewer children.
• The long-term decline in cervical cancer incidence is related to the widespread use of regular screening with Pap tests, which can detect both cancer precursors and early cancer; HPV vaccination is expected to contribute to further declines.

Mortality & Survival

What is mortality?

• Mortality is affected both by incidence and by prognosis .
• Two cancers may have similar survival rates but different mortality rates. For example, lung and esophageal cancer have similar survival, but lung cancer has a much higher mortality because of the high number of cases diagnosed.
• This means mortality may reflect both trends in underlying risk factors, and population-level or individual-level interventions such as screening and treatment.  
• Conversely, two cancers such as lung and colorectal cancers may occur with approximately equal frequency, but lung cancer is much more common as a cause of death because of its poorer survival.

Mortality rates for four most common cancers are mostly decreasing and are projected to continue to decline (Figure 3)

• Lung cancer was the most common cause of cancer death in Ontario for both males and females in 2007, and is projected to remain so between 2008 and 2011.
• Cancer mortality trends are different for men than for women, with the biggest difference for lung cancer.
• Lung cancer mortality for men has declined considerably since the late 1980s.
• For women, mortality rates from lung cancer are lower than for men, but they rose by 26% to an estimated 33 deaths per 100,000 population in the most recent years.
• Mortality from colorectal cancer is decreasing for both sexes and, like lung, is lower for women than for men.
• Mortality from both prostate and breast cancers has also declined.
• Declining mortality rates reflect improvements in prognosis attributable to screening and early detection, treatment, or both. 
  

What is relative survival?

• “Observed” survival is the proportion of people diagnosed with cancer who are still alive at a given number of months or years later.
• Relative survival is a ratio, comparing the survival experience of individuals with cancer to that of the general population of the same age and sex; it shows the extent to which cancer shortens life; it adjusts for the fact that the risk of death increases as we age.

Survival for most common cancers has improved (Figure 4)

• As a result of advances in screening and treatment, the relative survival ratio for most common cancers has improved.
• The exception is survival for urinary bladder cancer, for which the survival ratio has decreased over the past decade.
• In spite of improvements, relative survival for certain cancers still remains low.
• Most notable is relative survival for pancreas, lung and bronchus, and stomach cancers, for which relative survival remains less than 30%.
• On the positive side, survival for prostate, thyroid, melanoma of the skin, and female breast cancers is quite high—at 87% or higher relative survival five years after diagnosis.
• Prostate and thyroid cancer five-year survival ratios are both over 95%.

Prevalence

What is prevalence?

• Prevalence is the number of patients alive at any given time who have been diagnosed with cancer during a specific earlier timeframe.
• Both incidence and survival influence prevalence.
• A measure of the population burden of cancer, prevalence includes people in various phases:
• active treatment
• post-treatment in regular follow-up
• long-term survivors no longer in active cancer follow-up
• those being treated for recurrences
• those in palliative or end-of-life care

Prevalence is high for prostate and breast cancers (Figure 5)

• As of January 1, 2008, there were approximately 66,500 men in Ontario who had been diagnosed with prostate cancer within the last 10 years and 60,400 women in Ontario who had been diagnosed with breast cancer.
• Survival rates are high for these two cancers, which means prevalence for prostate and breast cancer is high.
• Prevalence for colorectal cancer is significantly lower, with about 38,600 cases diagnosed within the last 10 years in people still living in Ontario as of January 1, 2008.
• The low prevalence of colorectal cancer reflects fairly poor survival rates for this cancer.
• Of the most common cancers in Ontario, lung cancer has the lowest prevalence, reflecting poor lung cancer survival.
• In spite of increasing cancer incidence, more Ontarians are surviving cancer with every passing year because of more effective treatments and early detection.
• Many cancers are now being managed as chronic conditions.
• This hopeful news brings with it new challenges in terms of resources and services to meet the ongoing needs of people living with and beyond cancer.