Introduction
Lung cancer refers to the uncontrolled growth of the abnormal cells in one or both lungs. The growth occurs in the cells that line the air passages which then divide and form tumors. The human body produces new cells that replace the worn out body tissues. Under certain circumstances, cells may fail to grow but instead divide rapidly forming tumors in the lungs. The tumors start to grow and become larger thus lowering the ability of the lungs to provide sufficient oxygen to the bloodstream. When the tumors remain in one place without spreading to the other parts of the body, it is known as a benign tumor ( Hunt, Muers & Treasure, 2009 ). Such cells are not usually cancerous and may not be dangerous to human life. However, the more hazardous tumors are known as malignant, which consist of the cancerous cells capable of spreading to the other parts of the body. The process by which cancerous cells spread to the rest of the body parts from its point of origin is known as metastasis. Lung cancer which originates from the lungs is known as primary lung cancer. However, cancer may start from other parts of the body such as bones and then metastasize to the lungs. This is known as secondary lung cancer.
Epidemiology of Lung Cancer
Lung cancer remains the major cause of cancer deaths across many parts of the world compared to other cancer. Statistics show that lung cancer remains a major health threat and burden to both the developing and developed countries. According to the National Cancer Institute report of 2015, there was an estimated rate of 158040 cancer deaths in the United States of America. The survey by World Health Organization has also shown that a total of 7.6 million deaths occur globally every year due to cancer, with lung cancer being the leading, representing 13% of all the global deaths. The statistics show that lung cancer remains the leading cancer killer. In the UK, lung cancer deaths represent 6% of all the deaths with an estimated number of 38000 people being diagnosed annually ( Hunt, Muers & Treasure, 2009 ). The number of deaths from lung cancer in the UK is higher than that of bowel and breast cancer put together. While breast cancer is known to cause more deaths among women, statistics in the UK shows that more women die from lung cancer than breast cancer. Out of the total number of new diagnosis every year, only 25% of patients survive, meaning that out of every four patients diagnosed with lung cancer, three ends u dying. This statistics further shows how lung cancer is a serious health issue that requires serious attention.
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Types of Lung Cancer
Lung cancer is usually classified into two major types. Non-small cell lung cancer is the most common type of lung cancer, representing up to 80% of all the lung cancer cases. The other type is the small cell lung cancer which comprises only 20% of the diagnosis cases. The classification is mainly based on the appearance of the tumors and the size of the cells. This SCLC is majorly associated with cigarette smoking, and it can metastasize to many parts of the body. NSCLC, on the other hand, can further be divided into many types which include adenocarcinomas, large cell carcinoma and squamous cell carcinomas ( Cancer. Org , 2018 ). Adenocarcinomas are the most common kind of NSCLC representing 50%. It is common both in the people who smoke and those who do not smoke. Squamous cell carcinomas arise mainly in the central chest and represent about 30% of the NSCLC diagnosis. Large cell carcinomas are the least common type of NSCLC.
Risk factors and Causes of Lung Cancer
Lung cancer has a strong correlation to cigarette smoking. About 90% of the lung cancer cases arise due to tobacco smoking. As a person smokes many cigarettes, the chances of developing lung cancer also increase. A long period of smoking also increases the chance of individual developing lung cancer. Even though lung cancer also develops in those who do not smoke, the smokers are 25 times more likely to develop lung cancer than the non-smokers ( Hunt, Muers & Treasure, 2009 ). Tobacco smoke usually contains several chemicals many of which have been confirmed to be carcinogenic. The risk of a smoker developing lung cancer becomes high as an individual approaches 15 years of smoking. Passive smoking is also a confirmed risk factor for developing lung cancer. People who are non-smokers but constantly inhale smoke from the people smoking around them increase their chances of developing lung cancer. Passive smokers have a 25% increase in the risks of developing lung cancer compared to those who do not live next to people who smoke.
Carcinogens are one of the known causes of lung cancer among individuals. Carcinogens are a group of substances that can cause damage to the DNA thus facilitating the development of cancer. Some of the substances which contain carcinogens are asbestos, radiation, X-rays, and tobacco. Upon exposure to carcinogens, the bodies can form free radicals which then damage the cells making them unable to divide normally. Genetic disposition can also cause lung cancer. When a family has a history of lung cancer, there are possibilities that an individual can inherit a faulty gene which increases the chance of developing lung cancer ( Hunt, Muers & Treasure, 2009 ). Genetic disposition can either directly cause cancer or increase the risk when a person with faulty genes is exposed to certain risky environmental factors.
Symptoms of Lung Cancer
In the early stages, up to 25% of the lung cancer patients do not show any symptoms. During this time, the disease can be discovered through CT scan or chest X-ray. However, the invasion of cancer cells into the lung tissues may cause certain serious symptoms such as coughing, difficulty in breathing, chest pain, pneumonia and presence of blood in a cough ( Cancer Council, 2018 ). As cancer spreads to other parts, many other symptoms may be experienced including swollen lymph nodes, headaches, and seizures. A person may also feel fatigue, fever, general body weakness, pain in the joints and unexplained loss of weight. Symptoms usually vary from one person to the other, and the presence of such signs may not necessarily mean one has lung cancer. Continuous diagnosis and test are therefore necessary to ascertain the presence of lung cancer.
Diagnosis of Lung Cancer
The doctors can rely on the information revealed from the symptoms as well as other clinical procedures to diagnose lung cancer. One of the most common methods used to diagnose lung cancer is chest X-ray. Chest X-ray can show the presence of large tumors with up to 1 centimeter ( Cancer Council, 2018 ). However, small tumors may not be seen using X-ray, and therefore other methods are also preferred after undertaking a chest X-ray. If a patient has lung cancer, it may be visible as a mass that lies adjacent to other structures. Another method for diagnosing lung cancer is CT scans which are performed in the chest, brain, and abdomen. The CT scan aims to examine the presence of lung tumors. An X-ray beam is used to take pictures of the body parts to detect the presence of cancer tumors. CT scans can detect even the smaller tumors that X-ray cannot detect. It also provides details of the tumors present to help identify the type of lung cancer that is present.
PET scans are also another way the clinicians can use to diagnose lung cancer. However, this is mainly used after diagnosis is done with the core purpose of staging the lung cancer. It involves a specialized image testing that can appropriately stage lung cancer. The PET scans also measure the metabolic activity as well as the functions of the tissues. It helps to identify whether the tissue is growing normally and then determine the kind of cells present within the tumor. Magnetic Resonance Imaging (MRI) scans can also be used to diagnose lung cancer especially in situations where there is a need to have detailed information about the exact location of the tumor within the lungs. It uses magnetism and radio waves with a combination of computers to display body structures.
Treatment of Lung Cancer
The treatment of lung cancer usually depends on the type of cancer that a patient has and the stage of cancer. The major treatments for lung cancer usually involve surgical removal of the cancer tumor, radiation, and chemotherapy ( Kalemkerian et al., 2016 ). The surgical removal of the tumor is only done when the cancer is in stage one or two when cancer has not spread to many parts of the body. It is not always a better cure because some tumors may have spread to other body parts and continue to move. Radiotherapy is used to destroy the tumors in the lungs by passing high energy rays on the tumor cells. This high energy can destroy the cancer cells and eliminate them from the body completely ( Lung Cancer, 2018 ). This method, however, has several side effects such as damage to the normal cells. Chemotherapy, on the other hand, is used to produce chemicals that can interfere with the cell division thus damaging the DNA leading to the death of the cancer cells. It can produce chemicals which move throughout the body to kill all the tumor cells.
References
Cancer Council (2018). Retrieved from: https://www.cancercouncil.com.au/wp-content/uploads/2016/11/UC-Pub-Lung-CAN724-web-lo-res.pdf
Cancer. Org (2018). Retrieved from: https://www.cancer.org/cancer/non-small-cell-lung-cancer/about/what-is-non-small-cell-lung-cancer.html
Hunt, I., Muers, M. M., & Treasure, T. (Eds.). (2009). ABC of lung cancer (Vol. 79). John Wiley & Sons.
Kalemkerian, G. P., Donington, J. S., Gore, E. M., & Ramalingam, S. S. (Eds.). (2016). Handbook of Lung Cancer and Other Thoracic Malignancies . Springer Publishing Company.
Lung Cancer. (2018). Retrieved from: https://www.cancer.gov/types/lung
