Lung cancer epidemiology and demographics


 * Associate Editor(s)-In-Chief: Kim-Son H. Nguyen, M.D., M.P.A., Beth Israel Deaconess Medical Center, Harvard Medical School, Boston MA, ; Assistant Editor(s)-In-Chief: Michael Maddaleni, B.S.

Overview
Worldwide, lung cancer is the most common cancer in terms of both incidence and mortality with 1.35 million new cases per year and 1.18 million deaths, with the highest rates in Europe and North America. The population segment most likely to develop lung cancer is over-fifties who have a history of smoking. Lung cancer is the second most commonly occurring form of cancer in most western countries, and it is the leading cancer-related cause of death. Although the rate of men dying from lung cancer is declining in western countries, it is actually increasing for women due to the increased takeup of smoking by this group. Among lifetime non-smokers, men have higher age-standardized lung cancer death rates than women.

Smoking
Smoking, particularly of cigarettes, is by far the main contributor to lung cancer. In the United States, smoking is estimated to account for 87% of lung cancer cases (90% in men and 85% in women). Among male smokers, the lifetime risk of developing lung cancer is 17.2%. Among female smokers, the risk is 11.6%. This risk is significantly lower in non-smokers: 1.3% in men and 1.4% in women. It should also be noted that approximately 15 years after quitting smoking, the risk of lung cancer approaches that of a nonsmoker.

By the year 2030, the World Health Organization (WHO) projects that tobacco related deaths will hit an annual death rate of 3 million people in industrialized countries and 7 million in developing countries.

Radon Gas
Radon gas is the cause of approximately 15,000 to 22,000 deaths per year or 12% of the total number of lung cancer deaths per year. Radon gas is the second major cause of lung cancer behind smoking.

Radon gas levels vary by locality and the composition of the underlying soil and rocks. For example, in areas such as Cornwall in the UK (which has granite as substrata), radon gas is a major problem, and buildings have to be force-ventilated with fans to lower radon gas concentrations. The United States Environmental Protection Agency (EPA) estimates that one in 15 homes in the U.S. has radon levels above the recommended guideline of 4 picoCuries per liter (pCi/L). Iowa has the highest average radon concentration in the United States; studies performed there have demonstrated a 50% increased lung cancer risk with prolonged radon exposure above the EPA's action level of 4 pCi/L.

Asbestos
Asbestos related lung cancer is rarer than radon gas or smoking. It accounts for approximately 3,400 to 8,500 cases per year in the United States. In the UK, asbestos accounts for 2–3% of male lung cancer deaths.

Prevalence by Age
Lung cancer is more common in older adults. Smoking can cause eventual death over a significant period of time, which explains why it is rare in people under the age of 45. There is a clear correlation between an increase in the volume of smoking and the total number of lung cancer deaths. Studies have shown that there is approximately a 20 year lag period between smoking and death due to lung cancer (in men).

Prevalence by Geographic distribution
Eastern Europe has the highest lung cancer mortality among men, while northern Europe and the U.S. have the highest mortality among women. Lung cancer incidence is currently less common in developing countries. With increased smoking in developing countries, the incidence is expected to increase in the next few years, notably in China and India.