What is Lung Cancer?
How Tumors Form
The body is made up of many types of cells. Normally, cells grow, divide, and produce more cells as needed to keep the body healthy and functioning properly. Sometimes, however, the process goes wrong and cells become abnormal, forming more cells in an uncontrolled way. These extra cells form a mass of tissue, called a growth or tumor. Tumors can be benign, which means not cancerous, or malignant, which means cancerous. Lung cancer occurs when a tumor forms in the tissue of the lung.
The Leading Cause of Cancer Death
Lung cancer is the leading cause of cancer death in men and women in the United States. Experts estimate that over 200,000 new cases of lung cancer will be diagnosed each year-- over 100,000 cases in men and 100,000 cases in women. 150,000 Americans die of the disease each year. Lung cancer occurs most often between the ages of 55 and 65.
Two Major Types of Lung Cancer
There are two major types of lung cancer -- non-small cell lung cancer and small cell lung cancer. Each type of lung cancer grows and spreads in different ways, and each is treated differently.
- Non-small cell lung cancer is more common than small cell lung cancer.
- Small cell lung cancer grows more quickly and is more likely to spread to other organs in the body.
Lung Cancer Can Spread
Lung cancer may spread to the lymph nodes or other tissues in the chest, including the lung opposite to where it originated. It may also spread to other organs of the body, such as the bones, brain, or liver. When cancer spreads from its original location in the lung to another part of the body such as the brain, it is called metastatic lung cancer, not brain cancer. Doctors sometimes call this distant disease.
Smoking and Lung Cancer
Lung cancer would occur much less often if people did not smoke. The good news is that smoking is not as popular as it used to be. In 1965 about 42 percent of all adults smoked, but by 2008 only 21 percent did. Also, there has been a sharp drop in lung cancer deaths among men, mainly because fewer men are smoking, and for the first time in decades, lung cancer deaths in women are now declining.
The bad news is that smoking rates, which were dropping, have stopped declining in recent years. Smoking by young adults actually increased by 73 percent in the 1990s but has shown a downturn or leveling off in the past few years.
Causes and Risk Factors
Tobacco Products and Cancer
Using tobacco products has been shown to cause cancer. In fact, smoking tobacco, using smokeless tobacco, and being exposed regularly to secondhand tobacco smoke are responsible for a large number of cancer deaths in the U.S. each year.
Cigarette Smoking Causes Lung Cancer
Cigarette smoking is the number one cause of lung cancer. Scientists have reported widely on the link between cancer and smoking since the 1960s. Since then, study after study has provided more proof that cigarette smoking is the primary cause of lung cancer.
Before cigarette smoking became popular in the early part of the 20th century, doctors rarely, if ever, saw patients with lung cancer. But today, lung cancer is the leading cause of death by cancer. Over 85 percent of people with lung cancer developed it because they smoked cigarettes.
If You Smoke
If you smoke cigarettes, you are at much higher risk for lung cancer than a person who has never smoked. The risk of dying from lung cancer is 23 times higher for men who smoke and 13 times higher for women who smoke than for people who have never smoked. Lung cancer can affect young and old alike.
Stopping smoking greatly reduces your risk for developing lung cancer. After you stop, your risk levels off. Ten years after the last cigarette, the risk of dying from lung cancer drops by 50 percent -- which does not mean, however, that risk is eliminated.
Smoking cigars and pipes also puts you at risk for lung cancer. Cigar and pipe smokers have a higher risk of lung cancer than nonsmokers. Even cigar and pipe smokers who do not inhale are at increased risk for lung, mouth, and other types of cancer.
The likelihood that a smoker will develop lung cancer is related to the age smoking began; how long the person smoked; the number of cigarettes, pipes, or cigars smoked per day; and how deeply the smoker inhaled.
Other Factors That Increase Your Risk
- Many studies suggest that non-smokers who are exposed to environmental tobacco smoke, also called secondhand smoke, are at increased risk of lung cancer. Secondhand smoke is the smoke that non-smokers are exposed to when they share air space with someone who is smoking. Each year, about 3,000 non-smoking adults die of lung cancer as a result of breathing secondhand smoke.
- Exposure to radon can put a person at risk for lung cancer, too. People who work in mines may be exposed to this invisible, odorless, and radioactive gas that occurs naturally in soil and rocks. It is also found in houses in some parts of the country. A kit available at most hardware stores allows homeowners to measure radon levels in their homes.
- Another substance that can contribute to lung cancer is asbestos. Asbestos is used in shipbuilding, asbestos mining and manufacturing, insulation work, and brake repair, although products with asbestos have been largely phased out over the past several decades. If inhaled, asbestos particles can lodge in the lungs, damaging cells and increasing the risk for lung cancer. Asbestos workers should use the protective equipment provided by their employers and follow recommended work practices and safety procedures.
It's Never Too Late To Quit
Researchers continue to study the causes of lung cancer and to search for ways to prevent it. We already know that the best way to prevent lung cancer is to quit or never start smoking. The sooner a person quits smoking the better. Even if you have been smoking for many years, it's never too late to benefit from quitting.
Each U.S. state and territory has a free quitline to provide you with information and resources to help you quit smoking. To reach the quitline in your area, dial toll-free, 1-800-QUIT-NOW.
Symptoms and Diagnosis
Common Signs and Symptoms
When lung cancer first develops, there may be no symptoms at all. But as the cancer grows, it can cause changes that people should watch for. Common signs and symptoms of lung cancer include:
- a cough that doesn't go away and gets worse over time
- constant chest pain
- coughing up blood
- shortness of breath, wheezing, or hoarseness
- repeated problems with pneumonia or bronchitis
- swelling of the neck and face
- loss of appetite or weight loss
These symptoms may be caused by lung cancer or by other conditions. It is important to check with a doctor if you have symptoms because only a doctor can make a diagnosis. Don't wait to feel pain. Early cancer usually doesn't cause pain.
Tests for Lung Cancer
To find out if lung cancer may be present, the doctor evaluates a person's medical history, smoking history, their exposure to environmental and occupational substances, and family history of cancer.
The doctor also performs a physical exam and may order a test to take an image of the chest or other tests. Seeing a spot on an image is usually how a doctor first suspects that lung cancer may be present.
If lung cancer is suspected, the doctor may order a test called a sputum cytology. This is a simple test where a doctor examines a sample of mucous cells coughed up from the lungs under a microscope to see if cancer is present.
Biopsies to Detect Lung Cancer
But to confirm the presence of lung cancer, the doctor must examine fluid or tissue from the lung. This is done through a biopsy -- the removal of a small sample of fluid or tissue for examination under a microscope by a pathologist. A biopsy can show whether a person has cancer. A number of procedures may be used to obtain this tissue.
- Bronchoscopy -- The doctor puts a bronchoscope -- a thin, lighted tube -- into the mouth or nose and down through the windpipe to look into the breathing passages. Through this tube, the doctor can collect cells or small samples of tissue.
- Needle Aspiration -- The doctor numbs the chest area and inserts a thin needle into the tumor to remove a sample of tissue.
- Thoracentesis -- Using a needle, the doctor removes a sample of the fluid that surrounds the lungs to check for cancer cells.
- Thoracotomy -- Surgery to open the chest is sometimes needed to diagnose lung cancer. This procedure is a major operation performed in a hospital.
Doctors use imaging methods such as a spiral CT scan (also commonly known as helical CT) or a PET scan to look for signs of cancer. A CT scan, also known as computerized tomography scan, is a series of detailed pictures of areas inside the body. A PET scan, also known as positron emission tomography, is a computerized image of the metabolic activity of body tissues.
Other tests can include removal of lymph nodes for examination under a microscope to check for cancer cells. Lymph nodes are small, bean-shaped structures found throughout the body. They filter substances in a fluid called lymph and help fight infection and disease.
There are many treatment options for lung cancer, mainly based on the extent of the disease. The choice of treatment depends on your age and general health, the stage of the cancer, whether or not it has spread beyond the lung, and other factors.
If tests show that you have cancer, you should talk with your doctor and make treatment decisions as soon as possible. Studies show that early treatment leads to better outcomes.
Working With a Team of Specialists
A team of specialists often treats people with cancer. The team will keep the primary doctor informed about the patient's progress. The team may include a medical oncologist who is a specialist in cancer treatment, a surgeon, a radiation oncologist who is a specialist in radiation therapy, a thoracic surgeon who is a specialist in operating on organs in the chest, including the lungs, and others.
Before starting treatment, you may want another doctor to review the diagnosis and treatment plan. Some insurance companies require a second opinion. Others may pay for a second opinion if you request it.
Clinical Trials for Lung Cancer
Some lung cancer patients take part in studies of new treatments. These studies, called clinical trials, are designed to find out whether a new treatment is safe and effective.
Often, clinical trials compare a new treatment with a standard one so that doctors can learn which is more effective. People with lung cancer who are interested in taking part in a clinical trial should talk with their doctor.
The U.S. National Institutes of Health, through its National Library of Medicine and other Institutes, maintains a database of clinical trials at ClinicalTrials.gov.
Finding Out How Far Cancer Has Progressed
Once lung cancer has been found, it is usually staged. Staging means determining how far the cancer has progressed.
Through staging, the doctor can tell if the cancer has spread and, if so, to what parts of the body. Lung cancer often spreads to the brain or bones. Knowing the stage of the disease helps the doctor plan treatment.
Staging Small Cell and Non-Small Cell Lung Cancer
There are many types of lung cancer, but the two main types are "small cell" and "non-small cell." Small cell lung cancer is generally faster growing than non-small cell, but small cell is more likely to respond to chemotherapy.
Small cell lung cancer is divided into two stages. Limited stage is generally cancer confined to the chest and extensive stage is cancer that has spread outside the chest.
Non-small cell lung cancer is divided into four stages, I-IV. Most patients with stage I and II non-small cell tumors and some patients with stage III tumors can undergo surgery with the goal of cure.
Stage IV denotes cancer that has spread to other sites in the body, most often bone, brain, or liver. Most stage IV cancers cannot be cured, although treatment may be available to help prolong life.
Tests To Stage Lung Cancer
Here are the tests doctors use to stage lung cancer:
- Computed tomography, or CT scan, is a computer linked to an x-ray machine that creates a series of detailed pictures of areas inside the body.
- Magnetic resonance imaging, or MRI, is a powerful magnet linked to a computer that makes detailed pictures of areas inside the body.
- Radionuclide scanning uses a mildly radioactive substance to show whether cancer has spread to other organs, such as the liver.
- A bone scan uses a small amount of a radioactive substance to show whether cancer has spread to the bones.
- A mediastinoscopy or mediastinotomy can help show whether the cancer has spread to the lymph nodes in the chest by removing a tissue sample. The patient receives a general anesthetic for this procedure.
The choice of treatment depends on the type of lung cancer, whether it is non-small or small cell lung cancer, the size, location, the stage of the cancer, and the patient's general health.
Doctors may suggest many different treatments or combinations of treatments to control the cancer and/or improve the patient's quality of life.
What Standard Treatments Do
Here are the standard treatments for lung cancer:
- Surgery is an operation to remove the cancer. Depending on the location of the tumor, the surgeon may remove a small part of the lung, a lobe of the lung, or the entire lung and possibly even part of the ribcage to get to the lung.
- Chemotherapy uses anti-cancer drugs to kill cancer cells throughout the body. Doctors use chemotherapy to control cancer growth and relieve symptoms. Anti-cancer drugs are given by injection; through a catheter, a long thin tube temporarily placed in a large vein; or in pill form.
- Radiation therapy uses high-energy beams to kill cancer cells and shrink tumors. An external machine delivers radiation to a limited area, affecting cancer cells only in that area. Doctors may use radiation before surgery to shrink a tumor or after surgery to destroy any cancer cells remaining in the treated area.
- Photodynamic therapy, a newer technique, is laser therapy that is used in combination with a chemical to kill cancer cells. Doctors may use it to reduce symptoms of lung cancer, such as bleeding, or to treat very small tumors.
Treating Non-Small Cell Lung Cancer
Doctors treat patients with non-small cell lung cancer in several ways, and surgery is a common treatment. Cryosurgery, a treatment that freezes and destroys cancer tissue, may be used to control symptoms in the later stages of non-small cell lung cancer. Doctors may also use radiation therapy and chemotherapy to slow the progress of the disease and to manage symptoms.
Treating Small-Cell Lung Cancer
Small cell lung cancer spreads quickly. In many cases, cancer cells have already spread to other parts of the body when the disease is diagnosed. In order to reach cancer cells throughout the body, doctors almost always use chemotherapy.
Treatment for small cell lung cancer may also include radiation therapy aimed at the tumor in the lung or tumors in other parts of the body, such as in the brain. Surgery is part of the treatment plan for a small number of patients with small cell lung cancer.
Some patients with small cell lung cancer have radiation therapy to the brain even though no cancer is found there. This treatment, called prophylactic cranial irradiation or PCI, is given to prevent tumors from forming in the brain.
Researchers continue to look at new ways to combine, schedule, and sequence the use of chemotherapy, surgery, and radiation to treat lung cancer.
New Treatment Combinations
For instance, in one large study, patients with non-small cell lung cancer that had spread to nearby tissues or lymph nodes took radiation and chemotherapy at the same time instead of sequentially. Their five-year survival rates rose from about 6 percent to 16 percent.
Another study compared treatments given to two groups of people with small cell lung cancer. One group had chemotherapy plus two daily radiation treatments. The other had chemotherapy with only one daily radiation treatment.
Researchers found that the group receiving two daily radiation treatments with their chemotherapy had better survival rates.
Various combinations of the new drugs with traditional agents, such as cisplatin and carboplatin, are now either in clinical trials or have reported early results of the trials.
Other researchers are working to develop drugs called "molecularly targeted agents" which kill cancer cells by targeting key molecules involved in cancer cell growth. One of these drugs, called Avastin™, helped patients live a few months longer when it was combined with traditional chemotherapy.
New Ways to Schedule and Deliver Therapies
New ways to schedule and deliver radiation therapy are under study, too. In conformal radiotherapy, doctors try to assess the tumor in 3 dimensions and focus the beam of radiation directly on the area of the tumor.
With brachytherapy doctors can deliver radiation directly to the tumor using radioactive pellets that are inserted into the site of the tumor.
These two techniques -- conformal radiotherapy and brachytherapy -- have the advantage of reducing damage to surrounding tissue.
Detecting Lung Cancer Earlier
Researchers are constantly trying to come up with new ways to find and diagnose lung cancer in order to catch it and treat it in its earliest stages. The chest x-ray was one of the most common tools used to test for lung cancer. However, less than a third of lung cancer cases detected by chest x-ray were found early enough to be cured.
Because the benefits of chest x-ray were uncertain, in the summer of 2002, the National Cancer Institute launched a trial called the National Lung Screening Trial, or NLST, to determine if spiral CT was better than conventional x-ray at finding dangerous lung cancers and distinguishing between cancers and non-cancerous changes in the lungs, and ultimately, whether detecting these changes actually saves lives.
The initial results of the NLST, which was the only randomized clinical trial in the U.S. looking at this issue, came out in October 2010 and showed conclusively that spiral CT reduced the risk of dying by 20 percent compared to those who received a chest x-ray among heavy smokers. These results will be analyzed carefully over the next several years for cost effectiveness and other factors but currently only apply to current and former heavy smokers. It is not yet known if spiral CT will be an effective tool for detecting lung cancer in light or non-smokers.
There are also clinical trials under way to find out how well some substances can work to prevent an additional, secondary form of cancer in patients who have had early-stage lung cancer.
An aerosol spray to deliver drugs directly to the lungs and a vaccine for nicotine addiction are among the treatments researchers are studying. Common use of these treatments may be years away, however.
In December 2005, the National Cancer Institute and the National Human Genome Research Institute, both part of the National Institutes of Health, launched a project called The Cancer Genome Atlas (TCGA). The goal of TCGA is to increase our understanding of changes in genes that can lead to cancer. The project announced that lung cancer would be one of the first three cancers that would be studied. The overall goal of this project is to improve our ability to diagnose, treat, and prevent cancer.
Source: National Institutes of Health