lung cancer

What is lung cancer?

It can be devastating to find out that you or someone close to you has lung cancer. It's a serious illness in which some of the cells in your lungs have started to grow out of control, invading and destroying other cells. In the weeks and months to follow, you will probably have many different emotions, including anxiety about what lies ahead.

Almost before you have had time to take in what the doctors have told you, you will be offered a range of tests and treatments that aim to get rid of your cancer or relieve your symptoms, or both. The treatments you're offered will depend on the type of lung cancer you have, how large it is, and whether it has spread. A lot will also depend on how you feel about your illness and how you would like it to be treated.

If you are diagnosed with lung cancer, you will need to make some important decisions about your treatment.

We hope our information will answer your questions about lung cancer. It may also help you to talk with your doctor about the best treatments for you.

Some people want to know more about their cancer than others. Some will choose to have treatments that may help them live longer but which could have unpleasant, sometimes harmful, side effects. Other people prefer to enjoy as much of life as they can. 

There's no right or wrong way for you to deal with your cancer. The most important thing is for you to feel comfortable with the decisions you make. It's also essential that your medical team and those who care about you listen to what you say and respect your wishes.

Key points for people with lung cancer

• Lung cancer is the second most common type of cancer in both men and women (not counting skin cancer). It is the leading cause of death from cancer in the United States.
• By the time they are diagnosed, most people's lung cancer has spread outside of their lungs.
• You will be offered a range of treatments that aim to get rid of the cancer and improve your symptoms.
• Most treatments have side effects. These should be weighed against the benefits of the treatment.
• Cigarette smoking is the most common cause of lung cancer. The best way to prevent lung cancer is not to smoke.

Your lungs and what they do

You have two lungs. They sit in your chest, inside your rib cage, one on each side of your heart. They are covered by a layer of moist tissue called the pleura.

When you breathe in, your lungs fill with air.

Your lungs are a little like two spongy, elastic bags that fill up with air as you breathe in. They empty as you breathe out. The right lung is divided into three sections. These sections are called lobes. The left lung has two sections (or lobes).

Keeping your lungs healthy is important. They take oxygen from the air you breathe, which your blood then carries around your body. When you breathe out, they get rid of carbon dioxide, which is a waste product made by your body.

Here's how air travels into your lungs.

Your windpipe (trachea) is the air passage that leads from your throat into your chest. In your chest, your windpipe divides into two smaller airways (called bronchi). Each airway leads into a lung.

Inside your lungs, the airways divide into even smaller airways (called bronchioles). At the end of each of these smaller airways are little air sacs (called alveoli).

When you breathe in, air travels down your windpipe, through the airways, into your lungs and then into the smaller airways and the air sacs.

The air sacs in your lungs are connected to the network of blood vessels that surrounds your lungs. Oxygen from the air you breathe in passes through the thin walls of the air sacs and into these blood vessels. Then, the oxygen is carried back to your heart and pumped around your body. At the same time, carbon dioxide (which is made as a by-product of breathing) passes from your blood into the air sacs. The carbon dioxide leaves your body when you breathe out.

This is an X-ray picture of normal lungs. You can see the heart in the middle.

Also inside your chest, lying between your lungs, are:

• Your heart
• The main blood vessels that carry blood to and from your heart and the rest of your body
• The tube that carries food from your mouth to your stomach. This tube is called the esophagus.

What goes wrong in lung cancer?

When your body's cells are healthy, they divide, grow old, then die and are replaced in an orderly way. But when you get cancer, your cells grow and multiply too quickly.

In lung cancer, abnormal cells group together to form a lump called a tumor.

This means your cells don't have time to develop into normal, healthy cells. They may be the wrong shape and may not work properly. And they tend to lie on top of one another instead of in neat rows. Lung cancer can start almost anywhere in your lungs, but it usually starts in your airways. Abnormal cells tend to group together and form a lump, which is called a tumor. This slowly gets bigger.

Nearly all types of lung cancer can spread to other parts of your body and form more tumors. These are called secondary tumors. You may hear doctors talk about metastasis. This is the word doctors use to describe the way cancer spreads.

Types of lung cancer

Doctors divide lung cancer into two main kinds, based on what the cancer cells look like when examined in the laboratory.

The main types of lung cancer are:

Non-small-cell lung cancer (NSCLC). This is the most common kind. About 4 in 5 cases of lung cancer are this type. It can start in different parts of the lung. There are three different types of non-small-cell cancer.

• Adenocarcinoma: This kind of cancer grows in certain glands that produce mucus. It usually starts in the airways at the outer edges of the lungs. It is the most common type of non-small-cell lung cancer, making up about two-fifths of all cases of lung cancer.
• Squamous cell carcinoma: This is a slow-growing cancer that affects the airways. It makes up about one-third of all lung cancers.
• Large cell carcinoma: This type of cancer is made up of larger cells than other forms of lung cancer. About 15 percent of lung cancers are this type. ³

Small-cell lung cancer (SCLC). About 1 in 5 cases of lung cancer are this type. Doctors also call this sort of lung cancer oat cell cancer because it's made up of small cells that look like oats. These cells grow and spread more quickly than the cells in non-small-cell lung cancer.

Lung cancer: why me?

Some things increase your chance of getting lung cancer. Doctors call these things risk factors. Having a risk factor doesn't mean you'll definitely get lung cancer. It just means you're more likely to get it than someone who doesn't have the risk factor.

We've listed the main risk factors for lung cancer below. The most important is smoking. But sometimes people who have never smoked still get lung cancer.

If you think you have a high risk of getting lung cancer, you may wonder if there is some way of being tested that would catch lung cancer early, before it grows. This kind of test is called screening, but so far it hasn't been very successful for finding lung cancer.

Smoking

Smoking is responsible for 8 out of 10 deaths from lung cancer. Men who smoke are 22 times more likely to die from the disease than those who don't smoke. Women who smoke have a 12-fold greater risk of dying from lung cancer than nonsmokers.

Smoking leads to cancer because cells in the lung become damaged by poisonous chemicals in cigarette smoke. And, over time, these cells become cancerous.

How much you smoke is important, too. If you smoke less than half a pack per day, you're 15 times more likely to die from lung cancer than a nonsmoker. If you smoke one or two packs daily, you're 42 times more likely to die from lung cancer than someone who doesn't smoke.

Switching to a different brand with less tar or less nicotine does not make any difference to your risk of getting lung cancer. There's no such thing as a safer cigarette. The poisonous chemicals in smoke that can cause lung cancer are also found in marijuana cigarettes, so these are not a safe option.

Smoking cigars or a pipe also gives you a higher chance of getting lung cancer, even if you don't inhale.

Living or working in a smoky atmosphere makes it more likely you will get lung cancer, even if you don't smoke. This is called passive smoking. Living with a smoker increases your risk of lung cancer by one-third. ⁵ In 1990, the Environmental Protection Agency estimated that between 3,000 and 4,000 deaths from lung cancer were caused by passive smoking.

If you smoke or used to smoke, you may feel that this has caused your lung cancer and you may feel guilty. You may think other people blame you for getting lung cancer. You may even think that your doctor doesn't have much sympathy. But you shouldn't blame yourself for smoking. Nicotine is a highly addictive drug. And most people start smoking when they are teenagers and get addicted when they're too young to know any better. Also, some people with lung cancer have never smoked at all.

Being of a certain ethnic group

If you're African-American, you have a higher chance of getting lung cancer than a white American. Researchers think that this is because more African-Americans smoke, although there may also be a difference in the way their bodies deal with tobacco smoke. Researchers also think that African-Americans may, on average, have more fat in their diet. This could have an effect on their risk of getting lung cancer. ⁷ If you're African-American or native Hawaiian and smoke less than 30 cigarettes a day, you are more likely to get lung cancer than other groups of Americans who also smoke the same amount.

People who are Native American, Hispanic, Asian-American, or Japanese-American all have less lung cancer than average in the United States. These groups tend to smoke less, and the lower levels of lung cancer may also be linked to differences in diet and their genes (the inherited material in cells that controls how cells behave and grow). These tables show how common cancer is in different ethnic groups in the United States.

Men

Ethnic group	Number of lung cancer cases per 100,000 men
Native American	14
Hispanics, Japanese, Chinese, Filipinos, Koreans	42 to 53
Alaska Natives, Hawaiians, whites, Vietnamese	71 to 89
African-Americans	117

Women

Ethnic group	Number of lung cancer cases per 100,000 women
Japanese	15
Koreans, Filipinos, Hispanics, Chinese	16 to 25
African-Americans, Vietnamese, whites, Hawaiians	31 to 44
Alaska Natives	51

Being older

Lung cancer is more common in older people, probably because they have been smoking longer. In the United States, only around 2 in 100 people who have lung cancer are under age 45 when they get the disease.

Young people who get lung cancer tend to be heavy smokers who started smoking at a young age. They also tend to have a family history of the disease. ⁷

Working in certain industries

If you work with certain materials used in industry, you may have a higher chance of getting lung cancer. About 10 percent to 15 percent of lung cancer cases are probably due to working with cancer-causing substances, the most common of which is asbestos. 

All types of asbestos fibers cause lung cancer, but long-term exposure to types of asbestos called crocidolite or amosite carries the highest risk. It can take many years for the cancer to develop. The dangers of asbestos are now well-known, and there are laws governing how it is used. So there should be fewer lung cancers due to asbestos in the future.

Other chemicals that can cause lung cancer include arsenic and chromium. Nickel and vinyl chloride also carry a small risk. These substances are used in various industries, but there are laws about their use.

Living with radon

Radon is an invisible, odorless, and tasteless gas that is found naturally in soil and rocks. High levels of radon are found in buildings built on land that contains a lot of radon. If you live or work in one of these areas, you may have an increased chance of getting lung cancer.

The average concentration of radon in the home is 1.25 pCi/L, where pCi/L stands for picocuries (a measure of the amount of radon) per liter of air. Radon levels more than 4 pCi/L are considered unsafe. Although radon gas is thought to cause lung cancer, researchers haven't proved whether there is a link. 

Living with air pollution

Some studies have suggested there might be a link between air pollution and lung cancer. Researchers are trying to find out why this might be. If you breathe in certain particles from the air, they may damage the cells in your lungs. These damaged cells may become cancerous.

The main air pollutants are from motor vehicles, and include carbon monoxide, hydrocarbons, sulfur oxide, and nitrogen oxide. However, if pollution does cause cancer, the risk is tiny compared to the risk from smoking. Studies have shown that air pollution may cause less than 1 in 100 cases of lung cancer. 

Having other lung diseases

If you have one or more other persistent (chronic) lung diseases, such as tuberculosis, asthma, emphysema, or chronic bronchitis, you are slightly more likely to get lung cancer than other people.

If you smoke, you may have a condition called chronic obstructive pulmonary disease (COPD). If you have COPD, you are more likely to get lung cancer. ⁷ In COPD, not enough air flows into or out of the lungs. COPD is nearly always caused by smoking.

Having lung cancer in your family

If your parents, brothers, or sisters have had lung cancer, you are slightly more likely to get the disease than people with no family history. 

What stage is your lung cancer?

The TNM system is used to classify your lung cancer. It looks at three factors:

• T is for tumor
• N is for (lymph) nodes
• M is for metastasis. (Metastasis is when the cancer spreads to other parts of your body, such as your bones.)

Each factor is given a number. Generally, lower numbers mean your cancer is smaller and has not spread far (if at all).

• For T: The number tells you how big your cancer is and whether the cancer has spread outside the lung.
• For N: The number tells you whether your lung cancer has spread to your lymph nodes. Cancer cells can grow in the nodes and then travel from there to other parts of the body.
• For M: The number tells you whether your lung cancer has spread to other parts of your body.

The numbers are then sometimes followed by letters. These tell the doctor how the cancer was found and they give more detail about how far it has spread.

Here is an explanation of what each letter and number says about your cancer.

TNM		What it means
T (tumor)	TX	Cancer cells have been found but your doctor cannot find a tumor (lump).
	T0	There is no sign of lung cancer.
	Tis	Your tumor is only in the lining of the airway (in the bronchus or bronchiole). Doctors call this carcinoma in situ.
	T1	The size of your tumor is 3 centimeters (cm) or less.
	T2	Your tumor is more than 3 cm in size and it has started to grow into the covering around your lungs (pleura). But it is at least 2 cm from the point at which your windpipe (trachea) divides into the left and right airways (bronchi).
	T3	Your tumor has spread into the covering around the lungs (pleura) or chest wall and is less than 2 cm from the point at which the windpipe (trachea) divides into the left and right airways (bronchi).
	T4	Your tumor has spread to other tissues in your chest, such as your heart, your main blood vessels, your windpipe (trachea) or the tube that carries food to the stomach (esophagus). Or it is growing on the covering around the lung (pleura). This causes fluid containing cancer cells to build up around the lung.
N (nodes)	NX	Doctors can't tell if there's cancer in your lymph nodes. (You may not have been able to undergo the necessary tests.)
	N0	Your lung cancer has not spread to your lymph nodes.
	N1	Your lung cancer has spread to lymph nodes near your lung.
	N2	Your lung cancer has spread to lymph nodes in the middle of your chest.
	N3	Your lung cancer has spread to lymph nodes near your other lung or to lymph nodes above your collarbone.
M (metastasis)	MX	Doctors can't tell if your cancer has spread. (You may not have been able to undergo the necessary tests.)
	M0	Your lung cancer has not spread to another part of your body.
	M1	Your lung cancer has spread to another lobe of your lung or to another part of your body.

Key:

2 cm = 8/10 of an inch

3 cm = 1.2 inches

If your lung cancer is described as T1N1M0, it means that the tumor (lump) is 3 centimeters or smaller in size, has spread only to lymph nodes nearby and has not spread to other parts of your body.

Staging non-small-cell lung cancer

If you have non-small-cell lung cancer, doctors use the TNM system to stage your cancer on a scale of 0 through 4. Stage 0 is the least advanced stage of lung cancer (doctors call it carcinoma in situ) and stage 4 is the most advanced. Doctors call stage 1 and stage 2 lung cancer early disease. Stage 3A is called locally advanced disease, and stages 3B and 4 are advanced disease. Most people with lung cancer have advanced disease by the time they are diagnosed.

Here is an explanation of what stages 1 to 4 mean.

• Stage 1: The cancer is only in the lung.
• Stage 2: The cancer is small but has spread to the lymph nodes closest to the affected lung (stage 2A) or into the chest wall, the outer covering of the lung, the diaphragm or the outer covering of the heart (stage 2B).
• Stage 3: The cancer has spread to the lymph nodes further away from the affected lung but is still on the same side of the chest (stage 3A) or to the lymph nodes on the other side of the chest or collar bone, or to other places in the chest (stage 3B). Stage 3B can also mean that there is more than one tumor in the lung or that fluid around the lung (also known as pleural fluid) contains cancer cells.
• Stage 4: The cancer has spread to another lobe of the lung from where it started, or to other parts of the body (for example, the liver, or brain).

By the time they are diagnosed:

• A quarter of non-small-cell lung cancer patients have cancer that hasn't spread
• A fifth have cancer that has spread to nearby lymph nodes
• More than half have cancer that has spread to other distant parts of the body.

Staging small-cell lung cancer

If you have small-cell lung cancer, your doctors won't describe the stage in such a complicated way as for non-small-cell lung cancer. ¹⁶ They will describe the cancer as one of two types.

• Limited stage disease: The cancer is on one side of the chest
• Extensive stage disease: The cancer has spread beyond one side of the chest.

About two-thirds of people with small-cell lung cancer have extensive disease when they are diagnosed, and about one-third have limited stage disease.