What is a risk factor?

A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases, including cancers, have different risk factors.

Although these factors can increase a person's risk, they do not necessarily cause the disease. Some people with one or more risk factors never develop the disease, while others develop disease and have no known risk factors.

But, knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviors and being clinically monitored for the disease.

Cancer Types - Lung Cancer

What is lung cancer?

Lung cancer is cancer that usually starts in the lining of the bronchi (the main airways of the lungs), but can also begin in other areas of the respiratory system, including the trachea, bronchioles, or alveoli. It is the leading cause of cancer death in both men and women. In 2009, 219,440 new cases of lung cancer are expected, according to the American Cancer Society.

Lung cancers are believed to develop over a period of many years.

Nearly all lung cancers are carcinomas, cancers that begin in the lining or covering tissues of an organ. The tumor cells of each type of lung cancer grow and spread differently, and each type requires different treatment. About 85 percent to 90 percent of lung cancers belong to the group called non-small cell lung cancer.

Lung cancers are generally divided into two types:

  • Non-small cell lung cancer is much more common than small cell lung cancer. There are several types of non-small cell lung cancer, named for the type of cells found in the tumor:
    • Squamous cell carcinoma is also called epidermoid carcinoma. It often begins in the bronchi and usually does not spread as quickly as other types of lung cancer.
    • Adenocarcinoma usually begins along the outer edges of the lungs and under the lining of the bronchi. This type of non-small cell lung cancer begins in cells that have secretory (glandular) characteristics. It is the most common type of lung cancer in people who have never smoked.
    • Large cell carcinomas are a group of cancers with large, abnormal-looking cells. These tumors may begin anywhere in the lungs.
    • Adenosquamous carcinoma begins in flattened cells when viewed under a microscope. These cells also have secretory characteristics.
    • Undifferentiated carcinoma involves abnormal-looking cancer cells that tend to multiply quickly.
  • Small cell lung cancer, sometimes called oat cell cancer because the cancer cells may look like oats when viewed under a microscope, grows rapidly and quickly spreads to other organs. There are two stages of small cell lung cancer:
    • limited - cancer is generally found only in one lung. There may also be cancer in nearby lymph nodes on the same side of the chest.
    • extensive - cancer has spread beyond the primary tumor in the lung into other parts of the body.

It is important to find out what kind of lung cancer a person has. The different types of carcinomas, involving different regions of the lung, may cause different symptoms and are treated differently.

What are the symptoms of lung cancer?

The following are the most common symptoms for lung cancer. However, each individual may experience symptoms differently.

Lung cancer usually does not cause symptoms when it first develops, but they often become present after the tumor begins growing. A cough is the most common symptom of lung cancer. Other symptoms include:

  • constant chest pain
  • shortness of breath
  • wheezing
  • recurring lung infections, such as pneumonia or bronchitis
  • bloody or rust colored sputum
  • hoarseness
  • swelling of the neck and face caused by a tumor that presses on large blood vessels near the lung
  • pain and weakness in the shoulder, arm, or hand caused by a tumor that presses on certain nerves near the lung
  • fever for unknown reason

Like other cancers, lung cancer can cause:

  • fatigue
  • loss of appetite
  • loss of weight
  • headache
  • pain in other parts of the body not affected by the cancer
  • bone fractures

Other symptoms can be caused by substances made by lung cancer cells - referred to as a paraneoplastic syndrome. For example, certain lung cancer cells produce a substance that causes a sharp drop in the level of sodium in the blood, which can cause many symptoms, including confusion and sometimes even coma.

None of these symptoms is a sure sign of lung cancer. The symptoms of lung cancer may resemble another medical condition or problem. Always consult your physician for a diagnosis.

What are the risk factors for lung cancer?

A risk factor is anything that increases a person's chance of developing a disease such as cancer. Different cancers have different risk factors. Several risk factors make a person more likely to develop lung cancer:

  • Smoking is the leading cause of lung cancer, with nearly 90 percent of lung cancers thought to be a result of smoking.

Additional risk factors include:

  • secondhand smoke - breathing in the smoke of others
  • asbestos exposure
  • talcum powder
    While no increased risk of lung cancer has been found from the use of cosmetic talcum powder, some studies of talc miners and millers suggest a higher risk of lung cancer and other respiratory diseases from their exposure to industrial grade talc. Talcum powder is made from talc, a mineral that, in its natural form, may contain asbestos. Although, by law, all home-use talcum products (baby, body, and facial powders) have been asbestos-free since 1973.
  • cancer-causing agents in the workplace, including:
    • radioactive ores such as uranium
    • arsenic
    • vinyl chloride
    • nickel chromates
    • coal products
    • mustard gas
    • chloromethyl ethers
    • fuels such as gasoline
    • diesel exhaust
  • radon - a radioactive gas that cannot be seen, tasted, or smelled. It is produced by the natural breakdown of uranium.
  • personal or family history of lung cancer
  • air pollution
    In some cities, air pollution may slightly increase the risk of lung cancer.

How is lung cancer diagnosed?

In addition to a complete medical history (to check for risk factors and symptoms) and physical examination (to provide other information about signs of lung cancer and other health problems), procedures used to diagnose lung cancer may include:

  • chest x-ray - to look for any mass or spot on the lungs.
  • computed tomography scan (Also called a CT or CAT scan.) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.
  • sputum cytology - a study of phlegm (mucus) to look for cancer cells under a microscope.
  • needle biopsy - a needle is guided into the mass while the lungs are being viewed on a CT scan and a sample of the tissue is removed and evaluated in the pathology laboratory under a microscope. A lymph node biopsy may also be performed. Lymph nodes, located through out the body, serve as filters and also help to fight infection.
  • bronchoscopy - the examination of the bronchi (the main airways of the lungs) using a flexible tube (bronchoscope) passed down the mouth or nose. Bronchoscopy helps to evaluate and diagnose lung problems, assess blockages, obtain samples of tissue and/or fluid, and/or to help remove a foreign body.
  • mediastinoscopy - a process in which a small cut is made in the neck so that a tissue sample can be taken from the lymph nodes (mediastinal nodes) along the windpipe and the major bronchial tube areas to evaluate under a microscope.
  • positron emission tomography (PET) scan - radioactive-tagged glucose (sugar) is injected into the bloodstream. Tissues that use the glucose more than normal tissues (such as tumors) can be detected by a scanning machine. PET scans can be used to find small tumors or to check if treatment for a known tumor is working.
  • x-rays and scans of the brain, liver, bone, and adrenal glands - to determine if the cancer has spread from where it started into other areas of the body.

Other tests and procedures may be used as well.

Treatment for lung cancer:

Specific treatment for lung cancer will be determined by your physician based on:

  • your age, overall health, and medical history
  • extent of the disease
  • your tolerance for specific medications, procedures, or therapies
  • expectations for the course of the disease
  • your opinion or preference

Lung cancer may be treated with surgery, chemotherapy or other medications, radiation therapy, laser therapy, or a combination of treatments. "Combination treatment" or "multimodality treatment" refers to having more than one type of treatment.

Treatment for lung cancer includes one or more of the following:

  • surgery
    Three main types of surgery are most often used in lung cancer treatment. The choice depends on the size and location of the tumor in the lung, the extent of the cancer, the general health of the patient, and other factors.
    • segmental or wedge resection - removal of only a small part of the lung.
    • lobectomy - removal of an entire lobe of the lung.
    • pneumonectomy - removal of an entire lung.
  • radiation therapy
    Radiation therapy is the use of high-energy radiation to kill cancer cells and to shrink tumors. Radiation may also be used with chemotherapy to treat lung cancer. There are two ways to deliver radiation therapy, including the following:
    • external radiation (external beam therapy) - a treatment that precisely sends high levels of radiation directly to the cancer cells. The machine is controlled by the radiation therapist. Since radiation is used to kill cancer cells and to shrink tumors, special shields may be used to protect the tissue surrounding the treatment area. Radiation treatments are painless and usually last a few minutes.
    • internal radiation (brachytherapy, implant radiation) - radiation is given inside the body as close to the cancer as possible. Substances that produce radiation, called radioisotopes, may be swallowed, injected, or implanted directly into the tumor. Some of the radioactive implants are called “seeds” or “capsules."  Internal radiation involves giving a higher dose of radiation in a shorter time span than with external radiation. Some internal radiation treatments stay in the body temporarily. Other internal treatments stay in the body permanently, though the radioactive substance loses its radiation within a short period of time. In some cases, both internal and external radiation therapies are used.
  • chemotherapy
    The use of anticancer drugs to treat cancerous cells. In most cases, chemotherapy works by interfering with the cancer cell’s ability to grow or reproduce. Different groups of drugs work in different ways to fight cancer cells. The oncologist will recommend a treatment plan for each individual. Chemotherapy may be given before other treatments, after other treatments, or alone for lung cancer.
  • photodynamic therapy (PDT)
    A type of laser treatment that involves injecting photosensitizing chemicals into the bloodstream. Cells throughout the body absorb the chemicals. The chemicals collect and stay longer in the cancer cells, than in the healthy cells. At the right time, when the healthy cells surrounding the tumor may already be relatively free of the chemical, the light of a laser can be focused directly on the tumor. As the cells absorb the light, a chemical reaction destroys the cancer cells. For lung cancer, the light is delivered through a bronchoscope (a small, flexible tube with a light on the end) that is inserted through the mouth or nose.
  • targeted therapy
    As cancers grow, they form new blood vessels which nourish them. Research aimed at blocking the growth of these blood vessels has led to the development of medications called antiangiogenesis medications. Bevacizumab (Avastin®) is one of these medications. It has been found to be helpful in prolonging the survival of patients with advanced lung cancer. It is used with the standard chemotherapy regimen. Medications with other specific targets, such as erlotinib (Tarceva®) and cetuximab (Erbitux®), may also be useful.

There are specific names for the order in which treatment is given. Neoadjuvant treatment refers to having radiation or chemotherapy before surgery. Having one or both of these before surgery may help shrink the tumor - a smaller tumor is easier to take out in surgery.

Chemotherapy or radiation soon after surgery is called adjuvant treatment. The goal of adjuvant treatment is to kill any cancer cells that may be left after the surgery. Even if there is no sign of cancer cells, your physician may suggest adjuvant treatment, as it lowers the risk that the cancer may come back or spread.

Clinical trials are being conducted on prevention and treatment options for lung cancer, including photodynamic therapy and chemoprevention.

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