Causes of Lung Cancer

Fri, 15 Dec 2023

Main Causes of Lung Cancer

In most people, lung cancer is related to cigarette smoking. Smoking causes nearly 9 out of 10 cases (86%). A further 3% of cases of lung cancer are caused by exposure to second hand smoke in non smokers (passive smoking).

Here are some facts about smoking and lung cancer

• The more you smoke, the more likely you are to get lung cancer but it is the length of time you have been a smoker that is most important
• Starting smoking at a young age greatly increases the risk
• Filtered and low tar cigarettes might not increase your risk quite so much, but most smokers cancel this out by taking more, deeper puffs or smoking more cigarettes
• As soon as you stop smoking your risk of lung cancer starts to go down Passive smoking (breathing in other peoples cigarette smoke) increases the risk of lung cancer, but it is still much less than if you smoke yourself

It is almost impossible to work out the risk of occasional passive smoking. We know that the risk of lung cancer for passive smokers goes up the more cigarette smoke they are exposed to. Overall, people exposed to environmental tobacco smoke at work or at home have their risk of lung cancer increased by about a quarter compared to people who are not exposed to it. Heavy exposure to environmental tobacco smoke at work has been shown to double the risk of lung cancer.
Cigarette smoking is the main cause of lung cancer. But pipe and cigar smokers are still much more likely to get lung cancer than non smokers. They are also much more likely to get cancer of the mouth or lip.

Air Pollution

According to a study "Air pollution and lung cancer incidence in 17 European cohorts: prospective analyses from the European Study of Cohorts for Air Pollution Effects (ESCAPE)" published in The Lancet Oncology in 2013, particulate matter air pollution contributes to lung cancer incidence in Europe.

Air pollution in India is a serious issue with the major sources being fuel wood and biomass burning, fuel adulteration, vehicle emission and traffic congestion. India has a low per capita emissions of greenhouse gases but the country as a whole is the third largest after China and the United States. A 2013 study on non-smokers has found that Indians have 30% lower lung function compared to Europeans. Respirable particulate matter pollution remains a key challenge for India. Most Indian cities greatly exceed acceptable levels of suspended particulate matter. This may be because of refuse and biomass burning, vehicles, power plant emissions, industrial sources. In India, the use of coal for cooking and for heating the home, and a high level of smokiness in the home, has been shown to increase lung cancer risk.

Previous lung disease

Having had a disease that caused scarring in the lungs may be a risk factor for a type of lung cancer called adenocarcinoma of the lung. Tuberculosis (TB) can make scar tissue form in the lungs. A recent study in China showed that people who have had TB have double the risk of lung cancer. This risk continues for more than 20 years.

A family history of lung cancer

Researchers are looking into the impact of family history on lung cancer. It is likely that there is at least one faulty lung cancer gene that can be passed down in families (inherited). If you have a first degree relative with lung cancer your risk of lung cancer is increased by 51%. The risk is even greater if a brother or sister has lung cancer. This risk is regardless of whether or not you smoke. But families of smokers will all be exposed to cigarette smoke and so have an increased risk of lung cancer whether they have inherited a faulty gene or not.

Past cancer treatment

There is some evidence that particular cancer treatments might increase your risk of lung cancer. A review of lung cancer after treatment for breast cancer shows that ways of giving radiotherapy for breast cancer in the past increased the risk of developing lung cancer. But the most up to date methods of giving radiotherapy to treat breast cancer do not seem to increase the risk of primary lung cancer. Treatment for other types of cancer has also been linked to a slightly increased risk of lung cancer some years later. People may have an increased risk of lung cancer if they have had treatment for

• Hodgkin lymphoma
• Some types of non Hodgkin lymphoma
• Testicular cancer
• A type of cancer of the womb

Lowered immunity

HIV and AIDS lower immunity and so do drugs that people take after organ transplants. An overview of research studies shows that people with HIV or AIDS have a risk of lung cancer that is 3 times higher than people who do not have HIV or AIDS. People who take drugs to suppress their immunity after an organ transplant have double the usual risk of lung cancer. There is also an increased risk of lung cancer in people who have some auto-immune conditions. For example, research shows that systemic lupus erythematosus (SLE) may double the risk of lung cancer.