Lung cancer

Lung cancer

Lung cancer (both small cell and non-small cell) is the second most common cancer in both men and women (not counting skin cancer). In men, prostate cancer is more common, while in women breast cancer is more common. Lung cancer accounts for about 14% of all new cancers.
Lung cancer is by far the leading cause of cancer death among both men and women. Each year, more people die of lung cancer than of colon, breast, and prostate cancers combined.
Lung cancer mainly occurs in older people. About 2 out of 3 people diagnosed with lung cancer are 65 or older; fewer than 2% of all cases are found in people younger than 45. The average age at the time of diagnosis is about 71.
Overall, the chance that a man will develop lung cancer in his lifetime is about 1 in 13; for a woman, the risk is about 1 in 16. These numbers include both smokers and non-smokers. For smokers the risk is much higher, while for non-smokers the risk is lower.
Black men are about 40% more likely to develop lung cancer than white men. The rate is about the same in black women and in white women. Both black and white women have lower rates than men, but the gap is closing. The lung cancer rate has been dropping among men for many years and is just beginning to drop in women after a long period of rising.
Statistics on survival in people with lung cancer vary depending on the stage (extent) of the cancer when it is diagnosed.
Despite the very serious prognosis (outlook) of lung cancer, some people are cured. More than 350,000 people alive today have been diagnosed with lung cancer at some point.

How is lung cancer classified?

Lung cancer can be broadly classified into two main types based on the cancer's appearance under a microscope: non-small cell lung cancer and small cell lung cancer. Non-small cell lung cancer (NSCLC) accounts for 80% of lung cancers, while small cell lung cancer accounts for the remaining 20%.
NSCLC can be further divided into four different types, each with different treatment options:
• Squamous cell carcinoma or epidermoid carcinoma. As the most common type of NSCLC and the most common type of lung cancer in men, squamous cell carcinoma forms in the lining of the bronchial tubes.
• Adenocarcinoma. As the most common type of lung cancer in women and in nonsmokers, adenocarcinoma forms in the mucus-producing glands of the lungs.
• Bronchioalveolar carcinoma. This type of lung cancer is a rare type of adenocarcinoma that forms near the lungs' air sacs.
• Large-cell undifferentiated carcinoma. A rapidly growing cancer, large-cell undifferentiated carcinomas form near the outer edges or surface of the lungs.
Small cell lung cancer (SCLC) is characterized by small cells that multiply quickly and form large tumors that travel throughout the body. Almost all cases of SCLC are due to smoking.

What causes cancer?

Cancer is ultimately the result of cells that uncontrollably grow and do not die. Normal cells in the body follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and when this process breaks down, cancer begins to form. Unlike regular cells, cancer cells do not experience programmatic death and instead continue to grow and divide. This leads to a mass of abnormal cells that grows out of control.
Lung cancer occurs when a lung cell's gene mutation makes the cell unable to correct DNA damage and unable to commit suicide. Mutations can occur for a variety of reasons. Most lung cancers are the result of inhaling carcinogenic substances.

Carcinogens

Carcinogens are a class of substances that are directly responsible for damaging DNA, promoting or aiding cancer. Tobacco, asbestos, arsenic, radiation such as gamma and x-rays, the sun, and compounds in car exhaust fumes are all examples of carcinogens. When our bodies are exposed to carcinogens, free radicals are formed that try to steal electrons from other molecules in the body. These free radicals damage cells and affect their ability to function and divide normally.
About 87% of lung cancers are related to smoking and inhaling the carcinogens in tobacco smoke. Even exposure to second-hand smoke can damage cells so that cancer forms.

Genes

Cancer can be the result of a genetic predisposition that is inherited from family members. It is possible to be born with certain genetic mutations or a fault in a gene that makes one statistically more likely to develop cancer later in life. Genetic predispositions are thought to either directly cause lung cancer or greatly increase one's chances of developing lung cancer from exposure to certain environmental factors.

What are the symptoms of lung cancer?

Cancer symptoms are quite varied and depend on where the cancer is located, where it has spread, and how big the tumor is. Lung cancer symptoms may take years before appearing, usually after the disease is in an advanced stage.
Many symptoms of lung cancer affect the chest and air passages. These include:
• Persistent or intense coughing.
• Pain in the chest shoulder, or back from coughing.
• Changes in color of the mucus that is coughed up from the lower airways (sputum).
• Difficulty breathing and swallowing.
• Hoarseness of the voice.
• Harsh sounds while breathing (stridor).
• Chronic bronchitis or pneumonia.
• Coughing up blood, or blood in the sputum.
If the lung cancer spreads, or metastasizes, additional symptoms can present themselves in the newly affected area. Swollen or enlarged lymph nodes are common and likely to be present early. If cancer spreads to the brain, patients may experience vertigo, headaches, or seizures. In addition, the liver may become enlarged and cause jaundice and bones can become painful, brittle, and broken. It is also possible for the cancer to infect the adrenal glands resulting in hormone level changes.
As lung cancer cells spread and use more of the body's energy, it is possible to present symptoms that may also be associated with many other ailments. These include:
• Fever.
• Fatigue.
• Unexplained weight loss.
• Pain in joints or bones.
• Problems with brain function and memory.
• Swelling in the neck or face.
• General weakness.
• Bleeding and blood clots.

Lung Cancer Stages

The stage determines which choices will be available for treatment and informs prognosis. The most common cancer staging method is called the TNM system.
For non-small cell lung cancer, TNM descriptions lead to a simpler categorization of stages. These stages are labeled from I to IV, where lower numbers indicate earlier stages where the cancer has spread less. More specifically:
• Stage I is when the tumor is found only in one lung and in no lymph nodes.
• Stage II is when the cancer has spread to the lymph nodes surrounding the infected lung.
• Stage IIIa is when the cancer has spread to lymph nodes around the trachea, chest wall, and diaphragm, on the same side as the infected lung.
• Stage IIIb is when the cancer has spread to lymph nodes on the other lung or in the neck.
• Stage IV is when the cancer has spread throughout the rest of the body and other parts of the lungs.
Small cell lung cancer has two stages: limited or extensive. In the limited stage, the tumor exists in one lung and in nearby lymph nodes. In the extensive stage, the tumor has infected the other lung as well as other organs in the body.

How can lung cancer be prevented?

Cancers that are closely linked to certain behaviors are the easiest to prevent. For example, choosing not to smoke tobacco or drink alcohol significantly lowers the risk of several types of cancer - most notably lung, throat, mouth, and liver cancer. Even if you are a current tobacco user, quitting can still greatly reduce your chances of getting cancer. The most important preventive measure you can take to avoid lung cancer is to quit smoking.
Quitting smoking will also reduce your risk of several other types of cancer including esophagus, pancreas, larynx, and bladder cancer. If you quit smoking, you will usually reap additional benefits such as lower blood pressure, enhanced blood circulation, and increased lung capacity.
Exposure to tobacco smoke is not the only risk factor for lung cancer though. Those who have come into contact with asbestos, radon, and secondhand smoke also have an increased risk of developing lung cancer. In addition, having a family member who developed lung cancer without being exposed to carcinogens could mean that you have a genetic predisposition for developing the disease, increasing your overall risk.
Screening techniques are designed to find cancer at the earliest stage so that the most treatment options are available, increasing survival rates and avoiding highly invasive procedures. Most lung cancers are detected in the late stages of the disease after they have spread and are harder to treat. Although there currently do not exist approved screening tests for lung cancer that improve survival or detect localized disease

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Document by ACS