Lung Cancer

What is Lung Cancer?

Cancer is a class of diseases characterized by out-of-control cell growth, and lung cancer occurs when this uncontrolled cell growth begins in one or both lungs. Rather than developing into healthy, normal lung tissue, these abnormal cells continue dividing and form lumps or masses of tissue called tumors. Tumors interfere with the main function of the lung, which is to provide the bloodstream with oxygen to be carried to the entire body. If a tumor stays in one spot and demonstrates limited growth, it is generally considered to be benign.

More dangerous, or malignant, tumors form when the cancer cells migrate to other parts of the body through the blood or lymph system. When a tumor successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues, it is said to have metastasized. This process itself is called metastasis, and the result is a more serious condition that is very difficult to treat.
Lung cancer is called "primary" if the cancer originates in the lungs and "secondary" if it originates elsewhere in the body but has metastasized to the lungs. These two types are considered different cancers from diagnostic and treatment perspectives.
In 2007, about 15% of all cancer diagnoses and 29% of all cancer deaths were due to lung cancer. It is the number one cause of death from cancer every year and the second most diagnosed after breast and prostate cancers (for women and men, respectively). Lung cancer is usually found in older persons because it develops over a long period of time.

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.

How does lung cancer develop? - video

A short video explaining how lung cancer develops. Video by eHow.

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

How is lung cancer diagnosed and staged?

Physicians use information revealed by symptoms as well as several other procedures in order to diagnose lung cancer. Common imaging techniques include chest X-rays, bronchoscopy (a thin tube with a camera on one end), CT scans, MRI scans, and PET scans. Physicians will also conduct a physical examination, a chest examination, and an analysis of blood in the sputum. All of these procedures are designed to detect where the tumor is located and what additional organs may be affected by it.
Although the above diagnostic techniques provided important information, extracting cancer cells and looking at them under a microscope is the only absolute way to diagnose lung cancer. This procedure is called a biopsy. If the biopsy confirms lung cancer, a pathologist will determine whether it is non-small cell lung cancer or small cell lung cancer.
After a diagnosis is made, an oncologist will determine the stage of the cancer by finding out how far the cancer has spread. The stage determines which choices will be available for treatment and informs prognosis. The most common cancer staging method is called the TNM system. T (1-4) indicates the size and direct extent of the primary tumor, N (0-3) indicates the degree to which the cancer has spread to nearby lymph nodes, and M (0-1) indicates whether the cancer has metastasized to other organs in the body. A small tumor that has not spread to lymph nodes or distant organs may be staged as (T1, N0, M0), for example.
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.

Screening for lung cancer - video

A video tutorial discussing Lung Cancer and screening. Video by OncologyPodCasting.

How is lung cancer treated?

Lung cancer treatments depend on the type of cancer, the stage of the cancer (how much it has spread), age, health status, and additional personal characteristics. As there is usually no single treatment for cancer, patients often receive a combination of therapies and palliative care. The main lung cancer treatments are surgery, chemotherapy, and/or radiation. However, there also have been recent developments in the fields of immunotherapy, hormone therapy, and gene therapy.

Surgery

Surgery is the oldest known treatment for cancer. If a cancer is in stage I or II and has not metastasized, it is possible to completely cure a patient by surgically removing the tumor and the nearby lymph nodes. After the disease has spread, however, it is nearly impossible to remove all of the cancer cells.

Lung cancer surgery is performed by a specially trained thoracic surgeon. After removing the tumor and the surrounding margin of tissue, the margin is further studied to see if cancer cells are present. If no cancer is found in the tissue surrounding the tumor, it is considered a "negative margin." A "positive margin" may require the surgeon to remove more of the lung tissue.
Lung cancer surgery can be curative or palliative. Curative surgery aims to cure a patient with early stage lung cancer by removing all of the cancerous tissue. Palliative surgery aims to remove an obstruction or open an airway, making the patient more comfortable but not necessarily removing the cancer.
Surgery carries side effects - most notably pain and infection. Lung cancer surgery is an invasive procedure that can cause harm to the surrounding body parts. Doctors will usually provide several options for alleviating any pain from surgery. Antibiotics are commonly used to prevent infections that may occur at the site of the wound or elsewhere inside the body.

Radiation

Radiation treatment, also known as radiotherapy, destroys or shrinks lung cancer tumors by focusing high-energy rays on the cancer cells. This causes damage to the molecules that make up the cancer cells and leads them to commit suicide. Radiotherapy utilizes high-energy gamma-rays that are emitted from metals such as radium or high-energy x-rays that are created in a special machine. Radiation can be used as the main treatment for lung cancer, to kill remaining cells after surgery, or to kill cancer cells that have metastasized.
by: http://www.medicalnewstoday.com