What Causes Lung Cancer?

Lung Cancer occurs when the lung cells become abnormal and begin to grow out of control. As the cancer cells continue to evolve, there is a tendency for them to develop into a tumor thereby, spreading to various areas of the body.

The 2 main types of lung cancer are as follows:

• Non-Small Cell Lung Cancer (NSCLC): which constitute about 80% to 85% of lung cancers
• Small Cell Lung Cancer (SCLC): which constitute about 10% to 15%

While the causes of each Lung Cancer case may be unknown, the following risk factors help shed light on how some of these may lead to cancerous cells:

A. Smoking:

One of the leading causes of Lung Cancer- Tobacco Smoking, approximately causes 80% of cancer deaths. A seemingly strong risk factor, smoking often interacts with other factors to cause Lung Cancer. The other risk factors may include Radon, where Asbestos has an even higher risk. While every smoker may not be a victim of cancer, Genetics also play a crucial role alongside.

B. Non-smokers and Lung Cancer:

Lung Cancer may not necessarily always develop in smokers. Lung Cancer in non-smoking people could be caused due to the exposure to Radon gas, asbestos or other harmful chemicals, passive smoking, air pollution and other such factors.

However, a small percentage of Lung Cancers occurs in non-smoking people with no apparent cause or uncertified factors.

While Lung Cancers occur in differing ways in non-smokers as compared to smokers; the occurrence is typically observed in younger ages. Non-smokers experience certain gene changes during lung cancer, which differ from those found in smokers’ tumors. These changes, in some cases, may be relied upon to further guided treatment.

C. Lung Cancer caused due to the gene changes:

Research suggests how some of the risk factors could lead to certain changes in the DNA of lung cells; causing abnormal cell growth and at times, cancer. While DNA is the chemical found in our cells that constitutes the genes, thereby controlling the function of our cells; it can also have an influence on one’s risk for developing certain kinds of cancer.  

Certain genes exercise control when the cells are growing, dividing to make new cells:

1. Oncogenes: genes that help in growing, dividing, or keeping alive
2. Tumor Suppressor Genes: genes that facilitate keeping cell division under control or causing the cells to die at the right time

DNA changes that turn on oncogenes or turn off tumor suppressor genes is the root cause of some cancers to occur.

D. Lung Cancer caused due to the inherited gene changes:

DNA mutations or changes inherited from the parents may also increase the risk of developing certain types of cancers.  However, inherited mutations alone are not known to contribute to the number of lung cancer cases.

Nevertheless, the integral role of genes does come to play in cases of a history of lung cancer running in families. People with certain inherited DNA changes which typically exist in a certain chromosome have a higher risk of developing Lung Cancer, irrespective of whether they are smokers or non-smokers.  

Some people may generally be at a higher risk for Lung Cancer, owing to the fact that they may have inherited a lesser ability to break down or get rid of specific types of chemicals in the body which cause cancer.   

While others tend to inherit deficient DNA repair mechanisms, making them more prone to DNA changes; the presence of DNA repair enzymes which don’t work generally leads to these people becoming susceptible to the radiation as well as cancer-causing chemicals.

Tests which would help identify such people are being devised by researchers however, these tests are yet to be employed mainstream or consistently. Perhaps, abstinence from tobacco smoking and exposure to other such risk factors likely to increase cancer are recommended by doctors across.  

E. Lung Cancer caused due to the acquired gene changes:

Genetic changes that may cause Lung Cancer are may occur during a lifetime or may even be inherited. The mutations in the lung cells are often a result of exposure to environmental factors. However, few gene changes may be incidental that at times may occur inside of a cell, without any apparent cause.  

The acquired changes in specific genes- TP53 pr p16 tumor suppressor genes, K-RAS or ALK oncogenes are considered essential in developing non-small cell lung cancer. Changes observed in these genes as well as others may increase the likelihood of lung cancers to grow and/or spread.  Since not all Lung Cancers seem to share similar genetic changes; there exist gene changes yet to be found.