Introduction
Lung cancer is one of the leading causes of mortality and morbidity in the United States. Annually, it claims more lives than breast, ovarian, prostate, and colon cancers combined, which underscores its high prevalence rates. Smoking tobacco is the most important predisposing factor for lung cancer. Therefore, quitting smoking would reduce the risk of developing this health condition significantly.
Causes
The leading cause of lung cancer is cigarette smoking, with over 90 percent of such cases arising from the use of tobacco. The risk of developing lung cancer is directly proportional to the number of cigarettes smoked over a given time in what doctors refer to as the pack-years of smoking history – “The cumulative measurement of smoking and is generally calculated by multiplying average packs smoked per day by the duration of smoking, in years” (Nance et al., 2016, p. 113). Passive smoking is another leading cause of lung cancer, as non-smokers have a 24 percent chance of developing the health condition when exposed to secondary smoke. Exposure to asbestos fibers can cause lung cancer as they can persist in the lungs for a lifetime (De Groot, Wu, Carter, & Munden, 2018). People working with asbestos are thus likely to have lung cancer. Genetic susceptibility could also lead to lung cancer, as the condition has been shown to occur among non-smokers with a family history of the same.
Pathophysiology
Lung cancer originates in the lining of the bronchi in the epithelium of the respiratory tract when someone is exposed to carcinogens, such as tobacco smoke (VanMeter & Hubert, 2014). It starts as small cell carcinomas, commonly known as oat cell carcinoma, which grow rapidly, and thus by the time of diagnosis, they have already metastasized. These carcinomas occur centrally near the bronchi. Large cell carcinomas grow rapidly, they occur anywhere in the lungs, and they metastasize early in the disease. Women are prone to adenocarcinomas which attack the peripheral lung fields. Changes in lungs occur through the irritation of the epithelial wall, leaving cells exposed to irritants and inflammation (VanMeter & Hubert, 2014). After exposure to carcinogens, multistep carcinogenesis takes place to cause small cell lung cancer in neuroendocrine cells and non-small cell lung cancer in epithelial cells. In the brain, it causes headaches, pulmonary embolism in the circulatory system, weak bones, and muscle weakness.
Diagnosis
Diagnosis starts with simple screening procedures, such as low-dose computed tomography (LDCT), which makes detailed pictures of lungs using X-rays. If the doctor feels the need for further tests, sputum cytology could be used to check cancer cells in the mucus. Imaging tests could be used to detect growths in the lungs. Chest X-ray is the starting imaging test whereby low-dose radiation is used to image the lungs. Computed tomography (CT) is a powerful X-ray, and it can show the location, shape, and size of growth in the lungs (VanMeter & Hubert, 2014), and MRI could also be used. Positron emission tomography (PET) scan uses a special form of radiation, which can collect in the lungs before a camera is used to take images of the affected areas. Biopsy could also be used whereby some lung cells are removed and observed under a microscope for diagnosis.
Stages
Normally, cancer is grouped into four stages – stages I, II, III, and IV. In stage I, cancer is confined to the lungs with a size equal to or less than 3 centimeters (VanMeter & Hubert, 2014). At this point, metastasis has not started. In stage II, cancer has spread to the local lymph nodes, especially in the chest where it is confined. The tumor is larger than 3 cm but less or equal to 5 cm. In stage III, the tumor size is less or equal to 7 cm but larger than 5 cm. Cancer has also invaded the chest wall, parietal pericardium, and phrenic nerve. In stage IV, cancer has spread to other body parts, and it is bigger than 7 cm in size.
Treatment
The first treatment option is surgery, whereby the affected cells are removed surgically. However, while this is the most effective treatment option, it is limited to the early stages of the condition when the tumors have not spread from the lungs. Radiation can also be used whereby high-energy X-rays and protons are directed to kill cancer cells (VanMeter & Hubert, 2014). However, this option is not applicable in advanced stages whereby cancer has spread to other body parts. The third treatment is chemotherapy, whereby drugs are used to kill cancer cells. The drugs are administered orally or intravenously. The three treatment options could be used together where applicable for effective results.
Prognosis
In the US, 16.8 percent of people diagnosed with lung cancer survive for at least five years following diagnosis (National Cancer Institute, 2019). However, in other countries, the survival rates are low, with developing countries having the worst outcomes. By the time lung cancer becomes symptomatic, about 40 and 60 percent of NSCLC and SCLC, respectively, are in stage IV. The best prognosis is achieved if complete surgical resection is achieved at stage I. However, if diagnosed at stage IV, the five-year survival rate falls under 1 percent.
Conclusion
Lung cancer is among the leading causes of death in the US, and it is mainly caused by cigarette smoking even though genetic predisposition and exposure to industrial pollutants, such as asbestos, also contribute to its occurrence. It starts in the lungs and spreads to other body parts such as the brain, liver, and bones, and it could be diagnosed through imaging. It occurs in four stages, and its treatment involves surgery, chemotherapy, and radiotherapy.
References
De Groot, P. M., Wu, C. C., Carter, B. W., & Munden, R. F. (2018). The epidemiology of lung cancer. Translational Lung Cancer Research, 7(3), 220-233. Web.
Nance, R., Delaney, J., McEvoy, J. W., Blaha, M. J., Burke, G. L., Navas-Acien, A., … McClelland, R. L. (2016). Smoking intensity (pack/day) is a better measure than pack-years or smoking status for modeling cardiovascular disease outcomes. Journal of Clinical Epidemiology, 81, 111-119. Web.
National Cancer Institute. (2019). Cancer stat facts: Lung and bronchus cancer. Web.
VanMeter, K. C., & Hubert, R. J. (2014). Gould’s pathophysiology for the health professionals (5th ed.). St. Louis, MO: Elsevier.