Lung cancer is one of the deadliest of all cancers worldwide. It is common in both, men and women and it accounts for millions of new cases every year. It is also the most common cause of mortality with thousands of death every year worldwide.
Lungs are the main organs in the body system and are made up of 5 lobes, 3 in the right lungs and 2 in the left lung. As an individual breathes, the lungs absorb oxygen from the air which is then delivered to the rest of the body through the bloodstream. Lung cancer is a malignant tumour in which the cells grow in an uncontrolled way in one or both the lungs. Lung cancer starts in the lung tissues or cells lining the airways of the respiratory tract that allows the air to get into the lungs.
Causes of Lung Cancer
Cigarette smoking is considered to be the largest single cause of lung cancer. Tobacco smoke consists of thousands of chemicals and many of which are poison. These chemicals cause damage to the tissues and whenever people smoke, their body has to fight to heal the damage caused by the chemicals. Over time, the damage leads to the occurrence of the disease
When an individual inhales smoke, the chemicals reach the lungs quickly and from the lungs, it reaches the blood and is spread to other parts of the body.
Lung cancer consists of two types - small cell lung cancer and non-small cell lung cancer. Cigarette smoking is the predominant risk factor for both types of lung cancer. DNA damage is one of the main cause of the development of cancer and cigarette smoke exposure leads to the accumulation of carcinogens that results in DNA damage.
A large number of studies have been conducted to evaluate the effect of smoking cessation on the relative risk of lung cancer and a significant reduction in the relative risk of developing lung cancer was observed on people who quit smoking cigarettes. Quitting smoking has several benefits in patients having lung cancer.
2. Radon gas
Radon gas is defined as a radioactive gas that is released from the decay of uranium in rock and soil. When naturally occurring uranium breaks down, it produces radon gas. It is an invisible, odourless and tasteless gas that diffuses into the air. To some extent, it is present in all residential homes but in low concentration. It is naturally present in soil, rocks and building material from where it spreads with relative ease, mixing with other gases present in the atmosphere. Radon gas can also be found in water.
Radon is present in nearly all air and each of us breathes radon in every day, but in low concentration. However, those who inhale a high amount of radon are at higher risk of developing lung cancer. Radon can enter homes through cracks in floors, walls, or foundations and due to the closeness to the ground, basement and first floor have higher radon level as compared to other floors.
Asbestos is a mineral mined in the rocks which are found in amosite, crocidolite, and chrysotile, used in many industries. Multiple studies suggest that exposure to asbestos dust is associated with the development of various diseases, including lung cancer. In the lungs, the asbestos causes local inflammation and disrupts the orderly cell division.
The severity of asbestosis depends on the total amount of asbestos to which an individual has been exposed and the length of time since exposure first began. The fibres of asbestos can remain in the lungs for a long time and the tumour that can occur due to the presence of asbestos fibres in the lungs continues to develop for many years even after exposure stops. Usually, the lung cancer which is caused by asbestos is known as bronchial carcinomas.
The risk of developing lung cancer among workers who are exposed to both asbestos fibres and cigarette smoke is high and according to the reports, thousands of deaths have been caused by asbestos-related diseases.
4. Air pollution
Over the past decades, it has been observed that outdoor air pollution is linked to the development of different types of cancer, including lung cancer.
The total exposure to air pollution depends on indoor as well as outdoor. The indoor air quality has large health implications as people spend a considerable amount of time inside their homes. Indoor air pollution can become poisonous or unhealthy for an individual and some of the things that can make the indoor air pollution unhealthy include tobacco smoking, building materials, and oil gases.
Symptoms of Lung Cancer
Like all other diseases, the symptoms of lung cancer can also vary from one person to another and some of the symptoms are as follows:
- A cough that doesn’t go away
- Cough with a small amount of blood
- Shortness of breath
- Weight loss
- Extreme tiredness
Types of Lung Cancer
Lung cancer is primarily of two types:
1. Small Cell Lung Cancer
Small cell lung cancer is not a common type of lung cancer. This type of lung cancer begins in the middle of the lungs and it usually spreads early. It has the most aggressive clinical course and if it is left untreated, the median survival after diagnosis is only two to four months.
Small cell lung cancer is more aggressive as compared to non-small cell lung cancer and it grows more rapidly and quickly. The brain, bones and gastrointestinal tract are the most common sites of small cell lung cancer metastasis.
The key difference between the malignancies of small cell lung cancer and non-small cell lung cancer is that small cell lung cancer have neuroendocrine characteristics and on the other hand, non-small cell lung cancer is non-neuroendocrine. This means that small cell lung cancer can receive signals from neurons and release hormones into the blood but non-small cell lung cancer can’t receive signals.
2. Non-Small Cell Lung Cancer
Non-small cell lung cancer is a common type of lung cancer and it begins when the healthy cells in the lungs begin to grow uncontrollably and as a result, it forms a mass known as a tumour. This tumour can begin anywhere in the lungs and can be defined as cancerous or benign. Cancerous cancer is malignant and can spread to other parts of the body. On the other hand, benign cancer can grow but it can’t be spread to other parts of the body. Non-small cell lung cancer begins in the epithelial cells. Non-small cell lung cancer is further subdivided into three main types:
- Adenocarcinoma - Approximately 40% of lung cancer is adenocarcinoma and these tumours start in the cells that produce mucus.
- Squamous cell carcinoma - This type of non-small cell lung cancer develops in the cells that line the airways.
- Large cell carcinoma - This type of non-small cell lung cancer develops in all the cells, except cells that produce mucus and the cells that line the airways.
Non-small cell lung cancer has four main stages
Stage 1 - In the first stage, cancer is diagnosed in the lungs but has not spread outside the lung.
Stage 2 - In the second stage, cancer is found in the lungs along with nearby lymph nodes.
Stage 3 - In the third stage, cancer is found in the lungs and lymph nodes in the middle of the chest. Stage 3 is subdivided into two:
- Cancer is found in the lymph nodes but on the same side of the chest where cancer first started growing.
- Cancer is found in the lymph nodes but on the opposite side of the chest
Stage 4 - In the fourth stage, cancer is found on both sides if lungs, in the areas around the lungs and into the distant organs.
Risk factors associated with lung cancer
There are pieces of evidence that suggest that lung cancer results from damage to genes in the lung cells. This damage allows the cells to grow uncontrollably and eventually, leads to the development of lung cancer. While the exact cause of lung cancer is not fully understood but there are various risk factors that are associated with the development of this disease.
Tobacco exposure is the primary risk factor. People who smoke are 25 times more likely to develop lung cancer as compared to those who do not smoke. The association between tobacco smoke is strongest with small cell lung cancer as it is estimated that 98% of patients suffering from small cell lung cancer are smokers are have a history of cigarette smoking. The risk of developing lung cancer strongly depends on the age of an individual started smoking, for how long he/she is smoking and the number of cigarettes smoked. Studies also suggest that people who don’t smoke but who have been breathing in other’s tobacco smoke are also at risk of developing lung cancer.
Tobacco exposure is the strongest risk factor for lung cancer. Other than that, exposure to radiations, air pollution, steel, and coal gas also increases the risk of developing lung cancer. Sometimes, factor like family history can also cause this disease.