Cancer Cells

Cancer begins in cells, the building blocks that make up tissues. Tissues make up the organs of the body.

Normal, healthy cells grow and divide to form new cells as the body needs them. When normal cells grow old or become damaged, they die, and new cells take their place.

Sometimes, this orderly process goes wrong. New cells form when the body does not need them, and old or damaged cells do not die as they should. The build-up of extra cells often forms a mass of tissue called a growth or tumor.

Tumor cells can be benign (not cancer) or malignant (cancer). Benign tumor cells are usually not as harmful as malignant tumor cells:

•  Benign lung tumors

1.  are rarely a threat to life
2.  usually do not need to be removed
3.  do not invade the tissues around them
4.  do not spread to other parts of the body

 
 

• Malignant lung tumors

1. may be a threat to life
2. may grow back after being removed
3. can invade nearby tissues and organs
4. can spread to other parts of the body

Cancer cells spread by breaking away from the original tumor. They enter blood vessels or lymph vessels, which branch into all the tissues of the body. The cancer cells attach to other organs and form new tumors that may damage those organs. The spread of cancer is called metastasis.
 

Risk Factors

Doctors cannot always explain why one person develops lung cancer and another does not. However, we do know that a person with certain risk factors may be more likely than others to develop lung cancer. A risk factor is something that may increase the chance of developing a disease.

Studies have found the following risk factors for lung cancer:

• Tobacco smoke: Tobacco smoke causes most cases of lung cancer. It's by far the most important risk factor for lung cancer. Harmful substances in smoke damage lung cells. That's why smoking cigarettes, pipes, or cigars can cause lung cancer and why secondhand smoke can cause lung cancer in nonsmokers. The more a person is exposed to smoke, the greater the risk of lung cancer. For more information, see the NCI fact sheets Quitting Smoking and Secondhand Smoke.

•  Radon: Radon is a radioactive gas that you cannot see, smell, or taste. It forms in soil and rocks. People who work in mines may be exposed to radon. In some parts of the country, radon is found in houses. Radon damages lung cells, and people exposed to radon are at increased risk of lung cancer. The risk of lung cancer from radon is even higher for smokers. For more information, see the NCI fact sheet Radon and Cancer.

•  Asbestos and other substances: People who have certain jobs (such as those who work in the construction and chemical industries) have an increased risk of lung cancer. Exposure to asbestos, arsenic, chromium, nickel, soot, tar, and other substances can cause lung cancer. The risk is highest for those with years of exposure. The risk of lung cancer from these substances is even higher for smokers.

•  Air pollution: Air pollution may slightly increase the risk of lung cancer. The risk from air pollution is higher for smokers.

•  Family history of lung cancer: People with a father, mother, brother, or sister who had lung cancer may be at slightly increased risk of the disease, even if they don't smoke.

•  Personal history of lung cancer: People who have had lung cancer are at increased risk of developing a second lung tumor.

• Age over 65: Most people are older than 65 years when diagnosed with lung cancer.

Researchers have studied other possible risk factors. For example, having certain lung diseases (such as tuberculosis or bronchitis) for many years may increase the risk of lung cancer. It's not yet clear whether having certain lung diseases is a risk factor for lung cancer.


People who think they may be at risk for developing lung cancer should talk to their doctor. The doctor may be able to suggest ways to reduce their risk and can plan an appropriate schedule for checkups.

For people who have been treated for lung cancer, it's important to have checkups after treatment. The lung tumor may come back after treatment, or another lung tumor may develop.

Screening

Screening tests may help doctors find and treat cancer early. They have been shown to be very helpful in some cancers such as breast cancer. Currently, there is no generally accepted screening test for lung cancer.

Several methods of detecting lung cancer have been studied as possible screening tests. The methods under study include tests of sputum (mucus brought up from the lungs by coughing), chest x-rays, or spiral (helical) CT scans. You can read more about these tests in the Diagnosis section.

However, screening tests have risks. For example, an abnormal x-ray result could lead to other procedures (such as surgery to check for cancer cells), but a person with an abnormal test result might not have lung cancer.

Studies so far have not shown that screening tests lower the number of deaths from lung cancer. See "The Promise of Cancer Research" section for information about research studies of screening tests for lung cancer.

You may want to talk with your doctor about your own risk factors and the possible benefits and harms of being screened for lung cancer. Like many other medical decisions, the decision to be screened is a personal one. Your decision may be easier after learning the pros and cons of screening.
 

Symptoms

Early lung cancer often does not cause symptoms. But as the cancer grows, common symptoms may include:

• a cough that gets worse or does not go away
• breathing trouble, such as shortness of breath
• constant chest pain
• coughing up blood
• a hoarse voice
• frequent lung infections, such as pneumonia
• feeling very tired all the time
• weight loss with no known cause

Most often these symptoms are not due to cancer. Other health problems can cause some of these symptoms. Anyone with such symptoms should see a doctor to be diagnosed and treated as early as possible.
 

Diagnosis

Finding Lung Cancer Cells

Types of Lung Cancer

If you have a symptom that suggests lung cancer, your doctor must find out whether it's from cancer or something else. Your doctor may ask about your personal and family medical history. Your doctor may order blood tests, and you may have one or more of the following tests:

• Physical exam: Your doctor checks for general signs of health, listens to your breathing, and checks for fluid in the lungs. Your doctor may feel for swollen lymph nodes and a swollen liver.

•  Chest x-ray: X-ray pictures of your chest may show tumors or abnormal fluid.

•  CT scan: Doctors often use CT scans to take pictures of tissue inside the chest. An x-ray machine linked to a computer takes several pictures. For a spiral CT scan, the CT scanner rotates around you as you lie on a table. The table passes through the center of the scanner. The pictures may show a tumor, abnormal fluid, or swollen lymph nodes.

•  Finding Lung Cancer Cells

The only sure way to know if lung cancer is present is for a pathologist to check samples of cells or tissue. The pathologist studies the sample under a microscope and performs other tests. There are many ways to collect samples.

Your doctor may order one or more of the following tests to collect samples:

• Sputum cytology: Thick fluid (sputum) is coughed up from the lungs. The lab checks samples of sputum for cancer cells.

•  Thoracentesis: The doctor uses a long needle to remove fluid (pleural fluid) from the chest. The lab checks the fluid for cancer cells.

• Bronchoscopy: The doctor inserts a thin, lighted tube (a bronchoscope) through the nose or mouth into the lung. This allows an exam of the lungs and the air passages that lead to them. The doctor may take a sample of cells with a needle, brush, or other tool. The doctor also may wash the area with water to collect cells in the water.

•  Fine-needle aspiration: The doctor uses a thin needle to remove tissue or fluid from the lung or lymph node. Sometimes the doctor uses a CT scan or other imaging method to guide the needle to a lung tumor or lymph node.

•  Thoracoscopy: The surgeon makes several small incisions in your chest and back. The surgeon looks at the lungs and nearby tissues with a thin, lighted tube. If an abnormal area is seen, a biopsy to check for cancer cells may be needed.

• Thoracotomy: The surgeon opens the chest with a long incision. Lymph nodes and other tissue may be removed.

• Mediastinoscopy: The surgeon makes an incision at the top of the breastbone. A thin, lighted tube is used to see inside the chest. The surgeon may take tissue and lymph node samples.

Types of Lung Cancer

The pathologist checks the sputum, pleural fluid, tissue, or other samples for cancer cells. If cancer is found, the pathologist reports the type. The types of lung cancer are treated differently. The most common types are named for how the lung cancer cells look under a microscope:

• Small cell lung cancer: About 13 percent of lung cancers are small cell lung cancers. This type tends to spread quickly.
• Non-small cell lung cancer: Most lung cancers (about 87 percent) are non-small cell lung cancers. This type spreads more slowly than small cell lung cancer.

 

Treatment

• Surgery
• Radiation Therapy
• Chemotherapy
• Targeted Therapy

Your doctor may refer you to a specialist who has experience treating lung cancer, or you may ask for a referral. You may have a team of specialists. Specialists who treat lung cancer include thoracic (chest) surgeons, thoracic surgical oncologists, medical oncologists, and radiation oncologists.

Your health care team may also include a pulmonologist (a lung specialist), a respiratory therapist, an oncology nurse, and a registered dietitian.

Lung cancer is hard to control with current treatments. For that reason, many doctors encourage patients with this disease to consider taking part in a clinical trial. Clinical trials are an important option for people with all stages of lung cancer. See "The Promise of Cancer Research."

The choice of treatment depends mainly on the type of lung cancer and its stage. People with lung cancer may have surgery, chemotherapy, radiation therapy, targeted therapy, or a combination of treatments.

People with limited stage small cell lung cancer usually have radiation therapy and chemotherapy. For a very small lung tumor, a person may have surgery and chemotherapy. Most people with extensive stage small cell lung cancer are treated with chemotherapy only.

People with non-small cell lung cancer may have surgery, chemotherapy, radiation therapy, or a combination of treatments. The treatment choices are different for each stage. Some people with advanced cancer receive targeted therapy.

Cancer treatment is either local therapy or systemic therapy:

• Local therapy: Surgery and radiation therapy are local therapies. They remove or destroy cancer in the chest. When lung cancer has spread to other parts of the body, local therapy may be used to control the disease in those specific areas. For example, lung cancer that spreads to the brain may be controlled with radiation therapy to the head.
•  Systemic therapy: Chemotherapy and targeted therapy are systemic therapies. The drugs enter the bloodstream and destroy or control cancer throughout the body.

Your doctor can describe your treatment choices and the expected results. You may want to know about side effects and how treatment may change your normal activities. Because cancer treatments often damage healthy cells and tissues, side effects are common. Side effects depend mainly on the type and extent of the treatment. Side effects may not be the same for each person, and they may change from one treatment session to the next. Before treatment starts, your health care team will explain possible side effects and suggest ways to help you manage them.
 

Surgery

Surgery for lung cancer removes the tissue that contains the tumor. The surgeon also removes nearby lymph nodes.

The surgeon removes part or all of the lung:

• A small part of the lung (wedge resection or segmentectomy): The surgeon removes the tumor and a small part of the lung.
• A lobe of the lung (lobectomy or sleeve lobectomy): The surgeon removes a lobe of the lung. This is the most common surgery for lung cancer.
• All of the lung (pneumonectomy): The surgeon removes the entire lung.

After lung surgery, air and fluid collect in the chest. A chest tube allows the fluid to drain. Also, a nurse or respiratory therapist will teach you coughing and breathing exercises. You'll need to do the exercises several times a day.

The time it takes to heal after surgery is different for everyone. Your hospital stay may be a week or longer. It may be several weeks before you return to normal activities.

Medicine can help control your pain after surgery. Before surgery, you should discuss the plan for pain relief with your doctor or nurse. After surgery, your doctor can adjust the plan if you need more pain relief.

Radiation Therapy

Radiation therapy (also called radiotherapy) uses high-energy rays to kill cancer cells. It affects cells only in the treated area.

You may receive external radiation. This is the most common type of radiation therapy for lung cancer. The radiation comes from a large machine outside your body. Most people go to a hospital or clinic for treatment. Treatments are usually 5 days a week for several weeks.

Another type of radiation therapy is internal radiation (brachytherapy). Internal radiation is seldom used for people with lung cancer. The radiation comes from a seed, wire, or another device put inside your body.
The side effects depend mainly on the type of radiation therapy, the dose of radiation, and the part of your body that is treated. External radiation therapy to the chest may harm the esophagus, causing problems with swallowing.

You may also feel very tired. In addition, your skin in the treated area may become red, dry, and tender. After internal radiation therapy, a person may cough up small amounts of blood.

Your doctor can suggest ways to ease these problems.

Chemotherapy

Chemotherapy uses anticancer drugs to kill cancer cells. The drugs enter the bloodstream and can affect cancer cells all over the body.

Usually, more than one drug is given. Anticancer drugs for lung cancer are usually given through a vein (intravenous). Some anticancer drugs can be taken by mouth.

Chemotherapy is given in cycles. You have a rest period after each treatment period. The length of the rest period and the number of cycles depend on the anticancer drugs used.

You may have your treatment in a clinic, at the doctor's office, or at home. Some people may need to stay in the hospital for treatment.

The side effects depend mainly on which drugs are given and how much. The drugs can harm normal cells that divide rapidly:

• Blood cells: When chemotherapy lowers your levels of healthy blood cells, you're more likely to get infections, bruise or bleed easily, and feel very weak and tired. Your health care team gives you blood tests to check for low levels of blood cells. If the levels are low, there are medicines that can help your body make new blood cells.

•  Cells in hair roots: Chemotherapy may cause hair loss. Your hair will grow back after treatment ends, but it may be somewhat different in color and texture.

•  Cells that line the digestive tract: Chemotherapy can cause poor appetite, nausea and vomiting, diarrhea, or mouth and lip sores. Ask your health care team about treatments that help with these problems.

Some drugs for lung cancer can cause hearing loss, joint pain, and tingling or numbness in your hands and feet. These side effects usually go away after treatment ends.

When radiation therapy and chemotherapy are given at the same time, the side effects may be worse.

 

Targeted Therapy

Targeted therapy uses drugs to block the growth and spread of cancer cells. The drugs enter the bloodstream and can affect cancer cells all over the body. Some people with non-small cell lung cancer that has spread receive targeted therapy.

There are two kinds of targeted therapy for lung cancer:

• One kind is given through a vein (intravenous) at the doctor's office, hospital, or clinic. It's given at the same time as chemotherapy. The side effects may include bleeding, coughing up blood, a rash, high blood pressure, abdominal pain, vomiting, or diarrhea.
•  Another kind of targeted therapy is taken by mouth. It isn't given with chemotherapy. The side effects may include rash, diarrhea, and shortness of breath.

During treatment, your health care team will watch for signs of problems. Side effects usually go away after treatment ends.



Source:www.nih.gov
Last Editorial Review: 25/1/2010