Lung Cancer

What Is Lung Cancer?

Lung cancer is a type of cancer that starts in the lungs. Cancer starts when cells in the body begin to grow out of control. To learn more about how cancers start and spread.

Normal structure and function of the lungs:

1. • Your lungs are 2 sponge-like organs in your chest. Your right lung has 3 sections, called lobes. Your left lung has 2 lobes. The left lung is smaller because the heart takes up more room on that side of the body.
2. • When you breathe in, air enters through your mouth or nose and goes into your lungs through the trachea (windpipe). The trachea divides into tubes called bronchi, which enter the lungs and divide into smaller bronchi. These divide to form smaller branches called bronchioles. At the end of the bronchioles are tiny air sacs known as alveoli.
3. • The alveoli absorb oxygen into your blood from the inhaled air and remove carbon dioxide from the blood when you exhale. Taking in oxygen and getting rid of carbon dioxide are your lungs’ main functions.
4. • Lung cancers typically start in the cells lining the bronchi and parts of the lung such as the bronchioles or alveoli.
5. • A thin lining layer called the pleura surrounds the lungs. The pleura protects your lungs and helps them slide back and forth against the chest wall as they expand and contract during breathing.
6. • Below the lungs, a thin, dome-shaped muscle called the diaphragm separates the chest from the abdomen. When you breathe, the diaphragm moves up and down, forcing air in and out of the lungs.

Types of lung cancer

There are 2 main types of lung cancer

Non-small cell lung cancer (NSCLC)

About 80% to 85% of lung cancers are NSCLC. The main subtypes of NSCLC are adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. These subtypes, which start from different types of lung cells, are grouped together as NSCLC because their treatment and prognoses (outlook) are often similar.

Adenocarcinoma

Adenocarcinomas start in the cells that would normally secrete substances such as mucus. This type of lung cancer occurs mainly in people who smoke or used to smoke, but it is also the most common type of lung cancer seen in people who don't smoke. 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 the outer parts of the lung and is more likely to be found before it has spread. 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 carcinoma

Squamous cell carcinomas start in 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

Large cell carcinoma 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 (LCNEC), is a fast-growing cancer that is very similar to small cell lung cancer.

Small cell lung cancer (SCLC)

About 10% to 15% of all lung cancers are SCLC. It is sometimes called oat cell cancer. This type of lung cancer tends to grow and spread faster than NSCLC. In most people with SCLC, the cancer has already spread beyond the lungs at the time it is diagnosed. Since this cancer grows quickly.

Types of lung tumours

Along with the main types of lung cancer, other tumours can occur in the lungs.

Lung carcinoid tumours

Carcinoid tumours of the lung account for fewer than 5% of lung tumours. Most of these grow slowly. For more information about these tumours.

Other lung tumours

Other types of lung cancer such as adenoid cystic carcinomas, lymphomas, and sarcomas, as well as benign lung tumours such as hamartomas are rare. These are treated differently from the more common lung cancers and are not discussed here.

Cancers that spread to the lungs

Cancers that start in other organs (such as the breast, pancreas, kidney, or skin) can sometimes spread (metastasize) to the lungs, but these are not lung cancers. For example, cancer that starts in the breast and spreads to the lungs is still breast cancer, not lung cancer. Treatment for metastatic cancer to the lungs is based on where it started.

Risk Factors

A risk factor is anything that increases 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, cannot 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. These factors are related to the risk of lung cancer in general. It’s possible that some of these might not apply to small cell lung cancer (SCLC).

Risk factors you can change

Tobacco smoke

Smoking is by far the leading risk factor for lung cancer. About 80% of lung cancer deaths are thought to result from smoking, and this number is probably even higher for SCLC. It is very rare for someone who has never smoked to have SCLC. The risk of lung cancer for people who smoke is many times higher than for people who do not smoke. 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 may allow people to inhale more deeply.

Second-hand smoke

If you don’t smoke, breathing in the smoke of others (called second-hand smoke or environmental tobacco smoke) can increase your risk of developing lung cancer. Secondhand smoke is the third most common cause of lung cancer in the India.

Exposure to radon

Radon is a naturally occurring radioactive gas that results from the breakdown of uranium in soil and rocks. You cannot see, taste, or smell it. Radon is the second leading cause of lung cancer in our country, and it's the leading cause among people who don't smoke.

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.

Exposure to asbestos

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.

Exposure to other cancer-causing agents in the workplace

Other carcinogens (cancer-causing agents) found in some workplaces that can increase lung cancer risk include:

1. • Radioactive ores such as uranium
2. • Inhaled chemicals such as arsenic, beryllium, cadmium, silica, vinyl chloride, nickel compounds, chromium compounds, coal products, mustard gas, and chloromethyl ethers

Taking certain dietary supplements

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 people who smoked who took beta carotene supplements actually had an increased risk of lung cancer. The results of these studies suggest that people who smoke should avoid taking beta carotene supplements.

Arsenic in drinking water

Studies of people in parts of Asia 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 India, even areas where arsenic levels are above normal. For most Indian who are on public water systems, drinking water is not a major source of arsenic.

Risk factors you cannot change

Previous radiation therapy to the lungs

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 who have been treated for Hodgkin disease or women who get chest radiation after a mastectomy for breast cancer Women who have radiation therapy to the breast after a lumpectomy do not appear to have a higher-than-expected risk of lung cancer.

Air pollution

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 about 1% to 2% of all deaths from lung cancer in the India are thought to be due to outdoor air pollution.

Personal or family history 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 is 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). Researchers have found that genetics seems to play a role in some families with a strong history of lung cancer.

Factors with uncertain or unproven effects on lung cancer risk

Smoking marijuana

There are reasons to think smoking marijuana might increase lung cancer risk.

1. • Marijuana smoke contains tar and many of same cancer-causing substances that are in tobacco smoke. (Tar is the sticky, solid material that remains after burning, which is thought to contain most of the harmful substances in smoke.)
2. • Marijuana cigarettes (joints) are typically smoked all the way to the end, where tar content is the highest.
3. • Marijuana is inhaled very deeply and the smoke is held in the lungs for a long time, which gives any cancer-causing substances more opportunity to deposit in the lungs.
4. • Because marijuana is still illegal in many places, it may not be possible to control what other substances it might contain.

Those who use marijuana tend to smoke fewer marijuana cigarettes in a day or week than the amount of tobacco used by people who smoke cigarettes. 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 studies that have looked at past marijuana use in people who had lung cancer, most of the people who smoked marijuana 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.

E-cigarettes

E-cigarettes are a type of electronic nicotine delivery system. Most e-cigarettes contain nicotine, so the Food and Drug Administration (FDA) classifies them as "tobacco products." E-cigarettes are fairly new, and more research is needed to know what the long-term effects might be, including any possible increased risk of developing lung cancer.