3.3 Lung cancer

Show / hide chapter menu

3.0 Background

3.1 Tobacco—a leading preventable cause of death and disease

3.2 Cardiovascular diseases

3.3 Lung cancer

3.4 Respiratory diseases

3.5 Other cancers caused by or associated with smoking

3.6 Reproductive health and smoking

3.7 Pregnancy and smoking

3.8 Infant health and smoking

3.9 Increased susceptibility to infection in smokers

3.10 Eye diseases

3.11 Dental diseases

3.12 Gastrointestinal diseases

3.13 Bone density and risk of fractures

3.14 Effects of smoking on the skin

3.15 Smoking and complications in medical treatment

3.16 Smoking and diabetes

3.17 Poorer levels of general health

3.18 Smoking, motor vehicle crashes and other injuries

3.19 Burns and fires caused by tobacco use

3.20 Tobacco poisoning

3.21 Health effects for younger smokers

3.22 Genetic influences on tobacco-caused disease

3.23 Smoking, dementia and cognitive decline

3.24 Lung disease, smoking and occupational exposures

3.25 Air pollution, cigarette smoking and ill health

3.26 Health effects of smoking brands that claim to deliver lower levels of tar, nicotine and carbon monoxide

3.27 Health effects of smoking tobacco in other forms

3.28 Health 'benefits' of smoking?

3.29 Morbidity (ill health) attributable to tobacco-caused disease

3.30 Deaths attributable to tobacco by disease category

3.31 Morbidity and mortality due to tobacco-caused disease and socioeconomic disadvantage

3.32 Health effects of smoking other substances

3.33 Health effects of chewing tobacco, and of other smokeless tobacco products

3.34 Public perceptions of tobacco as a drug, and knowledge and beliefs about the health consequences of smoking

3.35 Health benefits of cessation

3.36 The global tobacco pandemic

Acknowledgments

References

Lung cancer is the term for a range of malignancies occurring in the respiratory tract, usually in the cells lining the airways of the lung. The four main types of lung cancer seen in smokers are squamous cell carcinoma, small cell undifferentiated carcinoma, adenocarcinoma, and large cell carcinoma.5 Despite medical advances, the prognosis for those diagnosed with lung cancer remains generally poor, with only about 11% of males and 14% of females surviving for five years after diagnosis.18

Cigarette smoking is by far the greatest cause of lung cancer and is largely responsible for causing the global pandemic of this disease (see Section 3.36). Lung cancer is the leading cause of cancer death among Australian men, and the second most common cause of cancer death in Australian women following breast cancer.19 It is estimated that active smoking is responsible for 88% of all lung cancer deaths in men aged over 35, and 75% in women of the same age.20

Exposure to cancer-causing chemicals in cigarette smoke causes genetic changes in cells lining the lungs and airways. Over time these damaged cells replicate themselves, forming a tumour and leading to the development of lung cancer.5 The risk of developing lung cancer is dose-related. Longer duration and heavier consumption patterns of tobacco use increase the likelihood of developing the disease. For example, a child who starts smoking aged 14 years or younger is five times more likely to die of lung cancer than a person who starts at the age of 24 or older, and 15 times more likely to die of lung cancer compared to someone who never smoked.21 Overall, smokers are 10 times more likely to die from lung cancer than are non-smokers, and heavy smokers are 15 to 25 times more at risk than non-smokers.22 Even at low consumption levels (one to four cigarettes per day), lung cancer death rates are elevated, the evidence being particularly strong for women.14

Recent research analysing lung cancer mortality in men and women living in Australia and New Zealand has found that female smokers appear to have about twice the risk of dying from lung cancer compared with male smokers.23 The Australian and New Zealand data, analysed as part of the Asia Pacific Cohort Studies Collaboration, tracked more than 83,000 adults and found that compared to non-smokers, men who smoked had about a 10-fold risk of dying of lung cancer, and women who smoked had an almost 20-fold risk. The authors speculate that this could be due to disparities in quitting behaviour between men and women,23 or as yet unclarified gender differences in smoking behaviour or susceptibility to toxins in cigarette smoke.24

The advent of filter tips, lower machine-measured toxin levels and other innovations in cigarette manufacture claimed to reduce exposure to harmful constituents from cigarette smoke have not had a significant effect on lung cancer death rates, but may have contributed to changes in the type of cancer most commonly diagnosed in smokers. Squamous cell carcinoma used to be the type of lung cancer most often seen in smokers in the early stages of the smoking epidemic, but now adenocarcinoma is the most frequently diagnosed cancer type. Although stopping smoking reduces the risk of developing lung cancer compared to continued smoking, an ex-smoker's risk of developing lung cancer remains higher than that of a never-smoker even after many years of cessation.5

In combination with some other substances (for example, asbestos), smoking greatly increases the chance of developing lung cancer and other respiratory diseases. See Section 3.24 for further discussion.

3.3.1 Past death rates for lung cancer

Because lung cancer due to smoking usually takes 20 or more years to develop and tobacco usage is the major factor in its causation, disease trends in the community are an important indicator of the smoking patterns of earlier decades. Figure 3.1 shows that early this century, lung cancer was a comparatively rare disease. Death rates began to rise steadily in males during the 1930s and 1940s,25 reflecting a large uptake of smoking among men from about 1910 through to the 1920s. This is consistent with what is known from other sources: that smoking of manufactured cigarettes became common at around the time of World War I, and that tobacco was freely supplied to the armed forces.1 (see also Chapter 1, Section 1.1). Men's lung cancer death rates peaked in the early 1980s and have since declined dramatically, reflecting the downturn in prevalence of male smoking since the second half of the last century. Latest data shows that in the period 2000–04, male lung cancer mortality fell to its lowest point since the 1960s.25

Men's death rates have always been greater than those of women, since men began smoking in large numbers prior to women, and have always had a higher smoking prevalence. Women did not take up smoking in appreciable numbers until the 1920s, with prevalence increasing over the following decades.1 Reflecting this behaviour, the upswing in lung cancer mortality in Australian women began during the 1930s and 1940s (Figure 3.1). During the 1960s, death rates were about double the rates of early in the century, and in the 25 years between 1964 and 1989, rates trebled. The rate of increase peaked during the 1990s, and according to the most recent data, now appears to be in decline.25

Declines in lung cancer mortality for both sexes are most influenced by reduced uptake of, and cessation of smoking. Although cessation, even after many years of smoking, reduces the risk of developing lung cancer, former smokers never quite reduce their risk to that of never smokers.26 This means that declines in lung cancer mortality lag two to three decades behind reductions in the prevalence of smoking due to quit behaviour.27 Restrictions in the machine-measured levels of tar, nicotine and carbon monoxide levels in cigarettes have not led to any decline in the risk of lung cancer in smokers.5