Causes and risk factors
Smoking is the cause of most cases of lung cancer. But there are other risk factors that can increase the chances of developing lung cancer.
Just because someone has a risk factor does not mean they will have cancer, and not having a risk factor does not mean they will not develop cancer.
Smoking is the cause of most cases of lung cancer and is the primary risk factor.
The more you smoke - and this includes cigarettes and pipes - the greater the risk. Around 90% of people with lung cancer are smokers or ex-smokers. The risk is greater if you start to smoke at an early age.
Lung cancer is more common in men than in women. However, the number of women with lung cancer is growing, as more and more women smoke.
People who don't smoke can also get lung cancer, though their risk is much lower. Nearly 10-15% of people who get lung cancer have never smoked.
- Second-hand smoke
Breathing in other people's cigarette smoke (second-hand smoking) can cause a slight increase in the risk of lung cancer. However, the risk is much lower when compared to actual smokers.
Lung cancer is more common in older people. Around 80% of lung cancers are diagnosed in people over 60. Lung cancer is uncommon in people under the age of 40.
People who have come into prolonged contact with asbestos (formerly used in construction industries) have a greater risk of developing lung cancer. These people have a higher risk if they smoke.
Asbestos exposure also increases the risk of mesothelioma, or cancer of the pleura.
- Previous cancer treatment
People who have received radiotherapy in the chest to treat any other previous cancer are at a slightly higher risk of developing lung cancer. The risk is higher if they smoke.
For these people, however, the risk of developing lung cancer is far outweighed by the benefits of their cancer treatment.
- Reduced immune response
Having a reduced immune system as a result of disease or treatment can increase the risk of developing lung cancer. People who have AIDS have weakened immune systems, and so do those who take drugs called immunosuppressants after having an organ transplant.
- Family risk
People who have an immediate family member who has had lung cancer may have a slightly increased risk.