Epidemiology

In the world today, lung cancer is the most common cancer and the leading cause of cancer death in men. It is also the third most common cancer (after breasts and colorectal cancers) and the second leading cause of cancer death (after breast cancer) in women. In 2008, lung cancer accounted for 13% or 1.6 million of total cancer cases and 18% or 1.4 million cancer-related deaths worldwide and also another 1.8 million cases in 2012, which accounted for 12.9% of the world’s total cancer incidence. The worldwide lung cancer mortality rate amounted to 1.59 million deaths in 2012, accounting for 19.4% of the total cancer deaths; thus making it the highest recorded cases and mortality rate from lung cancer. In 2018, the total cases of lung cancer had increased to 2.09 million in the world making it the number cancer cases, according to statistics by the World Health Organisation (WHO).

Over the last several decades, the incidence of adenocarcinoma of the lung has increased more rapidly than that of squamous cell carcinoma in men and especially in women. Adenocarcinoma has become the most common histologic cancer type diagnosed around the world since 2004, according to statistics from the World Health Organization. Sex differences in lung cancer mortality patterns also reflect historical differences between men and women in the increase and reduction of cigarette smoking over the last 50 years. In developing countries, not only the incidence but also the mortality rate of lung cancer has been increasing rapidly; incidence was ranked first in men and second in women.

Lung cancer incidence may also be related to air pollution caused by rapid and immature industrialization and continual increased use of automobiles in cities.

The global geographic distribution of lung cancer shows marked regional variation. In men, the highest incidence rates are observed in Central and Eastern Europe (53.5 per 100,000) and Eastern Asia (50.4 per 100,000). Notably low incidence rates are observed in Middle and Western Africa (2.0 and 1.7 per 100,000, respectively).

Causes and Risk Factors of Lung Cancer

Smoking is a known major risk factor for lung cancer but yet there are many etiological factors that can be seen as risk factors, and can be classed as changeable and non - changeable.

Risk Factors That One Can Change

• Tobacco Smoke: Tobacco smoking or smoking is the leading risk factor that has been associated with the lung cancer, causing about 80% of lung cancer deaths in the world today. Only in rare occasion do individuals who have never smoked get diagnosed with lung cancer. The risk associated with a smoker is far higher than for non-smokers. The risk of lung cancer increases with the number of cigarettes smoked each day and the number of years having smoked. Quitting at any age can significantly thee risk of developing lung cancer. 
• Secondhand Smoke: Some individuals who are non-smokers have been quite diagnosed with lung cancer. This is due to breathing in the smoke of others (called secondhand smoke or environmental tobacco smoke), which can increase the risk of developing lung cancer. Secondhand smoke is thought to cause more than 7,000 deaths from lung cancer each year. This should emphasis the need to ban smoking in public places.
• Exposure to Radon (Ionizing Radiation): Radon is produced by the natural breakdown of uranium in soil; rock and water that eventually becomes part of the air one breathe. Unsafe levels of radon can accumulate in any building, including homes; breathing it in exposes your lungs to small amounts of radiation, increasing a person’s risk of lung cancer. According to the US Environmental Protection Agency (EPA), radon is the second leading cause of lung cancer in the United States of America, and is the leading cause among non-smokers.
• Exposure to Asbestos: People who work with asbestos (such as in mines, a mill, textile plants, places where insulation is used and shipyards) are several times more likely to die of lung cancer. Lung cancer risk is much greater in workers exposed to asbestos who also smoke. It’s not clear how much low-level or short-term exposure to asbestos might raise lung cancer risk. People exposed to large amounts of asbestos also have a greater risk of developing mesothelioma, a type of cancer that starts in the pleura (the lining surrounding the lungs).
• Other Carcinogens: Also, carcinogens such as uranium, arsenic, beryllium, chromium compounds, and diesel exhaust, found in some workplaces, can also increase the chance of non-smokers to be diagnosed with lung cancer.
• Air Pollution: In cities, air pollution (especially near heavily trafficked roads) appears to raise the risk of lung cancer slightly. This risk is far less than the risk caused by smoking, but some researchers estimate that worldwide about 5% of all deaths from lung cancer may be due to outdoor air pollution. Reduction of air pollution using clean energy such as electric car, solar energy etc. can reduce the risk of lung cancer.

Risk Factors That Can’t Be Changed

• Previous Radiation Therapy to the Lungs: People who have had radiation therapy to the chest for other cancers are at higher risk for lung cancer, particularly if they smoke. Examples include people who have been treated for Hodgkin disease or women who get chest radiation after a mastectomy for breast cancer.
• Personal or Family History of Lung Cancer: For individuals who have had personal history of lung cancer, there is a high risk associated with developing lung cancer again. Individuals with brothers, sisters and parents who have had lung cancer have a slightly higher risk of lung cancer, especially if their relatives were diagnosed at a younger age. Researchers have found that genetics seems to play a role in some families with a strong history of lung cancer.

Prognosis

Despite the new diagnostic and genetic technologies that are now available and the many advances in surgical technique and biologic treatment, such as targeted treatment and immunotherapy, the overall 5-year survival rate of lung cancer in the world today is worse than before. Most lung cancer is discovered at an advanced stage, and the fact that only 15% of lung cancers are discovered in early stages may be responsible for the dismal prognosis. Therefore, early diagnosis by screening high-risk populations using low-dose computed tomography scan and effective biomarkers may improve the survival of lung cancer patients.

Prevention of Lung Cancer

In the prevention of lung cancer, there is no sure way but one can help reduce its risk if:

Avoid Smoking: For individuals who haven’t smoked, it is safe to avoid smoking at all cost being the major cause of lung cancer. And for people who smoke, one needs to quit smoking. Avoid areas where people smoke such as bars and restaurants, and seek out smoke free areas.

Preventing Air Pollution: This is done by reducing carbon emission using clean energy such as electric cars, solar power etc.

Radon Level Check: For individuals who live where uranium are usually found, it is safe to have one’s home checked for radon levels. High radon levels can be remedied to make home safer.

Avoid Carcinogens at Work: Taking safety precautions from toxic exposure at work is good. This can include using of a face mask for protection if provided with one at the office. The risk of lung damages from workplace carcinogens increases of an individual smokes.

Eating Diets Filled with Fruits and Vegetables: Choosing a healthy diet with a variety of fruits and vegetables is good for the body. Avoid taking large doses of vitamins in pill form, as some might be harmful.

Engage in Healthy Physical Activity: Exercising regularly and other physical activity can help reduce the risk associated with lung cancer.

N.B: Data for current world statistics on lung cancer among men, women and both sexes can be gotten from https://www.wcrf.org/int/cancer-facts-figures/data-specific-cancers/lung-cancer-statistics%20

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