November is Lung Cancer Awareness Month
There are three main types of lung cancer. Knowing which type you have is important because it affects your treatment options and your outlook (prognosis). If you aren’t sure which type of lung cancer you have, ask your doctor so you can get the right information.
Lung cancer is the second most common cancer in both men and women (not counting skin cancer), and 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.
Most lung cancers could be prevented, because they are related to smoking (or secondhand smoke), or less often to exposure to radon or other environmental factors. But some lung cancers occur in people without any known risk factors for the disease. It is not yet clear if these cancers can be prevented.
Most lung cancers have already spread widely and are at an advanced stage when they are first found. These cancers are very hard to cure. But in recent years, doctors have found a test that can be used to screen for lung cancer in people at high risk of the disease. This test can help find some of these cancers early, which can lower the risk of dying from this disease.
A risk factor is anything that affects a person’s chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, like smoking, can be changed. Others, like a person’s age or family history, can’t be changed.
But having a risk factor, or even several, does not mean that you will get the disease. And some people who get the disease may have few or no known risk factors.
Several risk factors can make you more likely to develop lung cancer.
Smoking is by far the leading risk factor for lung cancer. About 80% of lung cancer deaths are thought to result from smoking. The risk for lung cancer among smokers is many times higher than among non-smokers. The longer you smoke and the more packs a day you smoke, the greater your risk.
Cigar smoking and pipe smoking are almost as likely to cause lung cancer as cigarette smoking. Smoking low-tar or “light” cigarettes increases lung cancer risk as much as regular cigarettes. Smoking menthol cigarettes might increase the risk even more since the menthol allows smokers to inhale more deeply.
Secondhand smoke: If you don’t smoke, breathing in the smoke of others (called secondhand smoke or environmental tobacco smoke) can increase your risk of developing lung cancer. Secondhand smoke is thought to cause more than 7,000 deaths from lung cancer each year.
If you or someone you care about needs help quitting, see our Guide to Quitting Smoking or call the American Cancer Society at 1-800-227-2345.
Radon is a naturally occurring radioactive gas that results from the breakdown of uranium in soil and rocks. you can’t see, taste, or smell it. According to the US Environmental Protection Agency (EPA), radon is the second leading cause of lung cancer in this country, and is the leading cause among non-smokers.
Outdoors, there is so little radon that it is not likely to be dangerous. But indoors, radon can be more concentrated. Breathing it in exposes your lungs to small amounts of radiation. This may increase a person’s risk of lung cancer.
Homes and other buildings in nearly any part of the United States can have high indoor radon levels (especially in basements).
For more information, see Radon and Cancer.
People who work with asbestos (such as in mines, mills, textile plants, places where insulation is used, and shipyards) are several times more likely to die of lung cancer. Lung cancer risk is much greater in workers exposed to asbestos who also smoke. It’s not clear how much low-level or short-term exposure to asbestos might raise lung cancer risk.
People exposed to large amounts of asbestos also have a greater risk of developing mesothelioma, a type of cancer that starts in the pleura (the lining surrounding the lungs). For more on this type of cancer, see called Malignant Mesothelioma.
In recent years, government regulations have greatly reduced the use of asbestos in commercial and industrial products. It’s still present in many homes and other older buildings, but it’s not usually considered harmful as long as it’s not released into the air by deterioration, demolition, or renovation. For more information, see Asbestos and Cancer Risk.
Other carcinogens (cancer-causing agents) found in some workplaces that can increase lung cancer risk include:
The government and industry have taken steps in recent years to help protect workers from many of these exposures. But the dangers are still there, so if you work around these agents, you should be careful to limit your exposure whenever possible.
In cities, air pollution (especially near heavily trafficked roads) appears to raise the risk of lung cancer slightly. This risk is far less than the risk caused by smoking, but some researchers estimate that worldwide about 5% of all deaths from lung cancer may be due to outdoor air pollution.
Studies of people in parts of Southeast Asia and South America with high levels of arsenic in their drinking water have found a higher risk of lung cancer. In most of these studies, the levels of arsenic in the water were many times higher than those typically seen in the United States, even in areas where arsenic levels are above normal. For most Americans who are on public water systems, drinking water is not a major source of arsenic.
People who have had radiation therapy to the chest for other cancers are at higher risk for lung cancer, particularly if they smoke. Examples include people treated for Hodgkin diseaseor women who get radiation after a mastectomy for breast cancer. Women who get radiation therapy to the breast after a lumpectomy do not appear to have a higher than expected risk of lung cancer.
If you have had lung cancer, you have a higher risk of developing another lung cancer.
Brothers, sisters, and children of people who have had lung cancer may have a slightly higher risk of lung cancer themselves, especially if the relative was diagnosed at a younger age. It’s not clear how much of this risk might be due to shared genes among family members and how much might be from shared household exposures (such as tobacco smoke or radon).
Studies looking at the possible role of vitamin supplements in reducing lung cancer risk have had disappointing results. In fact, 2 large studies found that smokers who took beta carotene supplements actually had an increased risk of lung cancer. The results of these studies suggest that smokers should avoid taking beta carotene supplements.
Marijuana smoke
There are some reasons to think that smoking marijuana might increase lung cancer risk. Marijuana smoke has tar and many of the same cancer-causing substances that are in tobacco smoke. (Tar is the sticky, solid material that is left after burning, and is thought to have most of the harmful substances in smoke.)
Marijuana cigarettes (joints) are typically smoked all the way to the end, where tar content is the highest. Marijuana is also inhaled very deeply and the smoke is held in the lungs for a long time, which could give any cancer causing substances more opportunity to deposit in the lungs. And because marijuana is still illegal in many places, it may not be possible to control what other substances it might contain.
But those who use marijuana tend to smoke less marijuana in a day or week than the amount of tobacco consumed by cigarette smokers. The lesser amount smoked would make it harder to see an impact on lung cancer risk.
It’s been hard to study whether there is a link between marijuana and lung cancer because marijuana has been illegal in many places for so long, and it’s not easy to gather information about the use of illegal drugs. Also, in the studies that have looked at past marijuana use in people who had lung cancer, most of the marijuana smokers also smoked cigarettes. This can make it hard to know how much any increased risk is from tobacco and how much might be from marijuana. More research is needed to know the cancer risks from smoking marijuana.
Talc and talcum powder
Talc is a mineral that in its natural form may contain asbestos. Some studies have suggested that talc miners and millers might have a higher risk of lung cancer and other respiratory diseases because of their exposure to industrial grade talc. But other studies have not found an increase in lung cancer rate.
Talcum powder is made from talc. By law since the 1970s, all home-use talcum products (baby, body, and facial powders) in the United States have been asbestos-free. The use of cosmetic talcum powder has not been found to increase lung cancer risk.
Most lung cancers do not cause any symptoms until they have spread, but some people with early lung cancer do have symptoms. If you go to your doctor when you first notice symptoms, your cancer might be diagnosed at an earlier stage, when treatment is more likely to be effective. The most common symptoms of lung cancer are:
If lung cancer spreads to distant organs, it may cause:
Most of these symptoms are more likely to be caused by something other than lung cancer. Still, if you have any of these problems, it’s important to see your doctor right away so the cause can be found and treated, if needed.
Some lung cancers can cause syndromes, which are groups of very specific symptoms.
Cancers of the top part of the lungs (sometimes called Pancoast tumors) sometimes can affect certain nerves to the eye and part of the face, causing a group of symptoms called Horner syndrome:
The superior vena cava (SVC) is a large vein that carries blood from the head and arms back to the heart. It passes next to the upper part of the right lung and the lymph nodes inside the chest. Tumors in this area can press on the SVC, which can cause the blood to back up in the veins. This can lead to swelling in the face, neck, arms, and upper chest (sometimes with a bluish-red skin color). It can also cause headaches, dizziness, and a change in consciousness if it affects the brain. While SVC syndrome can develop gradually over time, in some cases it can become life-threatening, and needs to be treated right away.
Some lung cancers can make hormone-like substances that enter the bloodstream and cause problems with distant tissues and organs, even though the cancer has not spread to those tissues or organs. These problems are called paraneoplastic syndromes. Sometimes these syndromes can be the first symptoms of lung cancer. Because the symptoms affect organs other than the lungs, patients and their doctors may suspect at first that a disease other than lung cancer is causing them.
Some of the more common paraneoplastic syndromes associated with lung cancer are:
Again, many of these symptoms are more likely to be caused by something other than lung cancer. Still, if you have any of these problems, it’s important to see your doctor right away so the cause can be found and treated, if needed.
There are 2 main types of lung cancer:
There are subtypes of NSCLC, which start from different types of lung cells. But they are grouped together as NSCLC because the approach to treatment and prognosis (outlook) are often similar.
Adenocarcinoma: About 40% of lung cancers are adenocarcinomas. These cancers start in early versions of the cells that would normally secrete substances such as mucus.
This type of lung cancer occurs mainly in current or former smokers, but it is also the most common type of lung cancer seen in non-smokers. It is more common in women than in men, and it is more likely to occur in younger people than other types of lung cancer.
Adenocarcinoma is usually found in outer parts of the lung. Though it tends to grow slower than other types of lung cancer and is more likely to be found before it has spread, this varies from patient to patient.
People with a type of adenocarcinoma called adenocarcinoma in situ (previously called bronchioloalveolar carcinoma) tend to have a better outlook than those with other types of lung cancer.
Squamous cell (epidermoid) carcinoma: About 25% to 30% of all lung cancers are squamous cell carcinomas. These cancers start in early versions of squamous cells, which are flat cells that line the inside of the airways in the lungs. They are often linked to a history of smoking and tend to be found in the central part of the lungs, near a main airway (bronchus).
Large cell (undifferentiated) carcinoma: This type accounts for about 10% to 15% of lung cancers. It can appear in any part of the lung. It tends to grow and spread quickly, which can make it harder to treat. A subtype of large cell carcinoma, known as large cell neuroendocrine carcinoma, is a fast-growing cancer that is very similar to small cell lung cancer.
Other subtypes: A few other subtypes of NSCLC, such as adenosquamous carcinoma and sarcomatoid carcinoma, are much less common.
Large cell neuroendocrine carcinoma (LCNEC) is a rare cancer. It is a subtype of non-small cell lung cancer (NSCLC). Although it shares some features with SCLC (including a tendency to grow quickly), it is typically treated as a type of NSCLC.
The other 2 types of lung neuroendocrine tumors are carcinoids.
Typical and atypical carcinoid tumors look different under the microscope.
Carcinoids are sometimes also classified by where they form in the lung.
This distinction is important because the tumor’s location can affect which symptoms a patient has and may also affect how the tumor is treated.