Lung cancer is the most commonly diagnosed cancer and the leading cause of cancer death in Canada. In fact, more Canadians die of lung cancer than colorectal, pancreatic and breast cancers combined. In 2021 alone, an estimated 21,000 Canadians are expected to have died of lung cancer. The high rate of death (mortality rate) from lung cancer reflects both its high rate of diagnosis (incidence rate) and its low survival rate.
Staging is a way of classifying a cancer based on the extent of disease in the body at the time of diagnosis. Staging levels typically run from I to IV—the higher the number, the greater the spread of disease in the body from the origin of the cancer.
About half of all lung cancers are diagnosed at stage IV, at which point net survival is extremely low: five-year net survival is 4%. In contrast, about one in five lung cancers is diagnosed at stage I, where the cancer is relatively small and contained within the lung, and the five-year prognosis is much better (63%).
Lung cancer incidence and mortality rates increase dramatically with age. Incidence rates peak among Canadians aged 75 to 84 years (396 per 100,000 people), while mortality rates peak among Canadians aged 85 years and older (366 per 100,000 people). Overall, the incidence rate of lung cancer is 1/10 higher among men than women, and the mortality rate is almost 1/3 higher among men than women. However, for Canadians younger than 55 years of age, rates are higher among women than men.
While lung cancer incidence rates are generally higher among men than women, these rates have been getting closer over time. In 1992, the lung cancer incidence rate among men (109 per 100,000 men) was over twice that among women (52 per 100,000 women). However, by 2013, the gap had narrowed considerably (75 per 100,000 men versus 61 per 100,000 women) because of decreasing rates among men and increasing rates among women. Rates have subsequently been decreasing for both sexes, but more quickly among men, such that by 2018 the gap was smaller than ever (65 per 100,000 men versus 59 per 100,000 women).
The differences in lung cancer rates in men and women over time largely reflect past differences in tobacco smoking. The prevalence of daily smoking among men began to decline in the mid-1960s, preceding the decrease in lung cancer incidence by about 20 years. Among women, the decrease in daily smoking did not start until the 1980s. Trends in lung cancer mortality rates largely follow trends in lung cancer incidence.
Approximately 1 in 10 Canadians reported smoking cigarettes on a regular basis in 2020, with Canadians aged 25 and older being almost three and a half times more likely to report being a current smoker (11%) than those aged 15 to 19 (3%). Smoking was more prevalent among men than women, with 12% of men reporting that they were current smokers, compared with 9% of women.
A recent study by Health Canada used urinary cotinine (COT) measures and questionnaire data from the Canadian Health Measures Survey to examine secondhand smoke exposure for nonsmokers aged 6 to 79. Among Canadian nonsmokers, over one-fifth (22%) reported having been regularly exposed to secondhand smoke, and, of those, one-quarter (26%) had detectable COT levels. The most important contributor to elevated COT was exposure “at home.”
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