November is Lung Cancer awareness month. What better time to find out all you need to know about it. Lung cancer is the leading cause of cancer deaths in both men and women worldwide.
The two types of lung cancer, they grow and spread differently:
Non-small cell lung cancers (NSCLC).
This is the most common type of lung cancer, making up 80-85% of all cases. It grows and spreads more slowly than small cell lung cancer (SCLC). NSCLC is staged based on the size of the primary tumor and if and where the cancer has spread (stages I, II, III, IV). Some lung cancer tumore are composed of cells from more than one type of NSCLC. There are different kinds of NSCLC; common ones are Adenocarcinoma, squamous cell carcinoma, large cell carcinoma, large cell neuroendocrine tumors etc.
Small cell lung cancers (SCLC)
Small Cell Lung Cancer (SCLC) makes up 15-20% of all lung cancer cases. It is a type of neuroendocrine tumor with cells that are smaller in size than most other cancer cells. It is a fast-growing cancer that rapidly to other parts of the body. Some lung cancer tumors contain cells that are both SCLC and a form of NSCLC, Often large cell. SCLC is usually staged as either limited or extensive, depending on if, and where, the cancer has spread. Examples are Mesothelioma and Carcinoid tumors.
Causes & Risk Factors of Lung Cancer
The exact cause of lung cancer is still being investigated. Certain risk factors have been shown to play a part in causing cells to become cancerous.
The incidence of lung cancer is strongly correlated with cigarette smoking, with about 90% of lung cancers arising as a result of tobacco use. The risk of lung cancer increases with the number of cigarettes smoked and the time over which smoking has occurred; doctors refer to this risk in terms of pack-years of smoking history (the number of packs of cigarettes smoked per day multiplied by the number of years smoked). For example, a person who has smoked two packs of cigarettes per day for 10 years has a 20 pack-year smoking history. Among those who smoke two or more packs of cigarettes per day, one in seven will die of lung cancer.
Pipe and cigar smoking also can cause lung cancer, although the risk is not as high as with cigarette smoking. Thus, while someone who smokes one pack of cigarettes per day has a risk for the development of lung cancer that is 25 times higher than a nonsmoker, pipe and cigar smokers have a risk of lung cancer that is about five times that of a nonsmoker.
Passive smoking or the inhalation of tobacco smoke by nonsmokers, who share living or working quarters with smokers, is also an established risk factor for the development of lung cancer. Research has shown that nonsmokers who reside with a smoker have a 24% increase in risk for developing lung cancer when compared with nonsmokers who do not reside with a smoker.
Exposure to asbestos fibers
Asbestos fibers are silicate fibers that can persist for a lifetime in lung tissue following exposure to asbestos. The workplace was a common source of exposure to asbestos fibers, as asbestos was widely used in the past as both thermal and acoustic insulation. Today, asbestos use is limited or banned in many countries. Cigarette smoking drastically increases the chance of developing an asbestos-related lung cancer in workers exposed to asbestos; asbestos workers who do not smoke have a five-fold greater risk of developing lung cancer than nonsmokers, but asbestos workers who smoke have a risk that is fifty- to ninety-fold greater than nonsmokers.
Exposure to radon gas
Radon gas is a natural radioactive gas that is a natural decay product of uranium that emits a type of ionizing radiation. Radon gas is a known cause of lung cancer, with an estimated 12% of lung-cancer deaths attributable to radon gas. As with asbestos exposure, concomitant smoking greatly increases the risk of lung cancer with radon exposure. Radon gas can travel up through soil and enter homes through gaps in the foundation, pipes, drains, or other openings. Radon gas is invisible and odorless, but it can be detected with simple test kits.
Exposure to diesel exhaust
Exhaust from diesel engines is made up of gases and soot (particulate matter). Many occupations, such as truck drivers, toll booth workers, forklift and other heavy machinery operators, railroad and dock workers, miners, garage workers and mechanics, and some farm workers are frequently exposed to diesel exhaust. Studies of workers exposed to diesel exhaust have shown a small but significant increase in the risk of developing lung cancer.
Air pollution from vehicles, industry, and power plants can raise the likelihood of developing lung cancer in exposed individuals. Up to 1%-2% of lung cancer deaths are attributable to breathing polluted air, and experts believe that prolonged exposure to highly polluted air can carry a risk for the development of lung cancer similar to that of passive smoking.
While the majority of lung cancers are associated with tobacco smoking, the fact that not all smokers eventually develop lung cancer suggests that other factors, such as individual genetic susceptibility, may play a role in the causation of lung cancer. Numerous studies have shown that lung cancer is more likely to occur in both smoking and nonsmoking relatives of those who have had lung cancer than in the general population. It is unclear how much of this risk is due to shared environmental factors (like a smoking household) and how much is related to genetic risk. People who inherit certain genes, like genes that interfere with DNA repair, may be at greater risk for several types of cancer. Tests to identify people at increased genetic risk of lung cancer are not yet available for routine use.
The presence of certain diseases of the lung, notably chronic obstructive pulmonary disease (COPD), is associated with an increased risk (four- to six-fold the risk of a nonsmoker) for the development of lung cancer even after the effects of concomitant cigarette smoking are excluded. Pulmonary fibrosis (scarring of the lung) appears to increase the risk about seven-fold, and this risk does not appear to be related to smoking.
Prior history of lung cancer
Survivors of lung cancer have a greater risk of developing a second lung cancer than the general population has of developing a first lung cancer. Survivors of non-small cell lung cancers have an additive risk of 1%-2% per year for developing a second lung cancer. In survivors of small cell lung cancers, the risk for development of second lung cancers approaches 6% per year.
Symptoms of lung cancer are varied depending upon where and how widespread the tumor is. Warning signs of lung cancer are not always present or easy to identify. Lung cancer may not cause pain or other symptoms in some cases. A person with lung cancer may have the following kinds of symptoms:
- No symptoms: patients with small, single masses often report no symptoms at the time the cancer is discovered.
- Symptoms related to the cancer: difficulty breathing, cough, shortness of breath, wheezing, chest pain, and coughing up blood (hemoptysis), shoulder pain in some cases or paralysis of the vocal cords leading to hoarseness, difficulty swallowing (dysphagia). If a large airway is obstructed, collapse of a portion of the lung may occur and cause infections (abscesses, pneumonia) in the obstructed area.
- Symptoms related to metastasis: Excruciating pain at the sites of bone involvement. Cancer that has spread to the brain may cause a number of neurologic symptoms that may include blurred vision, headaches, seizures, or symptoms of stroke such as weakness or loss of sensation in parts of the body.
- Hormonal symptoms
- Nonspecific symptoms: weight loss, weakness, and fatigue.
- Psychological symptoms: Depression and mood changes.
When should one consult a doctor?
One should consult a health-care professional if he or she develops the symptoms associated with lung cancer, particularly if they have
- A new persistent cough or worsening of an existing chronic cough,
- Blood in the sputum,
- Persistent bronchitis or repeated respiratory infections,
- chest pain,
- Unexplained weight loss and/or fatigue,
- Breathing difficulties such as shortness of breath or wheezing.
Treatment of lung cancer can involve a combination of surgery, chemotherapy, targeted therapy, immunotherapy, and radiation therapy as well as newer experimental methods.
Smoking cessation is the most important measure that can prevent the development of lung cancer.