Lung cancer is the second most common cancer in the United States.

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What is lung cancer?

Lung cancer is a disease in which malignant (or dangerous) cells form in the tissue of the lungs. As more of these cells are produced, they can form into a tumor and spread to the surrounding body tissue, lymph nodes, and bloodstream.

Lung cancer is the leading cause of cancer deaths for both men and women and the second most common cancer in the United States. More than 222,000 new cases of lung cancer are diagnosed each year in the U.S., and more than 155,000 people die from the disease annually. There are two main types of lung cancer: non-small cell and small cell lung cancer. Although smoking is the leading cause of lung cancer, other risk factors include a family history of the disease and exposure to radiation, asbestos, and arsenic.

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Causes of lung cancer

There are many possible causes of lung cancer, but the biggest risk factor by far is smoking tobacco. Other risk factors include exposure to secondhand smoke, radon, and asbestos. Here are the most common lung cancer causes.

Smoking cigars, cigarettes, and pipes. Smoking accounts for as many as 80% of lung cancers in women and 90% of lung cancers in men. According to the National Cancer Institute (NCI), women who smoke are 13 times more likely and men who smoke are 23 times more likely to develop the disease than those who never smoked.

The smoke from tobacco contains at least 70 carcinogens—i.e., chemicals that are known to cause cancer. Cigars contain similar types of carcinogens, but in some cases, the chemicals are present in higher amounts. Some of these compounds, called tobacco-specific-nitrosamines (TSNAs), are thought to be among the most cancer-causing substances on Earth.

Although smokeless tobacco products like snuff and chewing tobacco are less dangerous than cigarettes, according to the American Cancer Society (ACS), they still contain harmful chemicals (including high levels of TSNAs) and can also be deadly.

It’s unclear whether people can get lung cancer from smoking marijuana. One research review published in 2016 in the journal Cancer Epidemiology, Biomarkers & Prevention didn’t find a link between marijuana use and lung cancer, a result that the researchers called “somewhat surprising,” especially because marijuana and tobacco smoke both contain similar amounts of certain carcinogens. But the researchers also noted that marijuana’s THC (the chemical delta-9-tetrahydrocannabinol, which gives users a “high” and is also used medicinally) may in fact counter the effects of cancer-causing carcinogens. The ACS says that more research is needed to see whether the benefits of legalizing marijuana for medicinal purposes outweigh the negatives, but the organization does oppose smoking or vaping marijuana, since the smoke can be harmful.

Secondhand smoke. It’s also possible to get lung cancer from secondhand smoke, or smoke from other people’s cigars and cigarettes. Even if you’re not using the tobacco product yourself, you’re still inhaling the carcinogens, albeit in smaller amounts. The Centers for Disease Control and Prevention (CDC) estimates that each year, about 7,300 people who have never smoked before die of lung cancer caused by secondhand smoke.

Radon. As the second leading cause of lung cancer and the leading cause among non-smokers, radon—an invisible, odorless, and tasteless gas that’s found naturally in rocks and dirt—is responsible for about 20,000 cases of lung cancer each year. It can build up in homes and other buildings. You can test your home for radon and take steps to reduce your exposure. Find a test kit through the National Radon Program Services.

Family history. As is the case with other diseases, lung cancer can run in the family. The NCI says that if you’ve had a relative who’s been diagnosed with lung cancer, you may be up to twice as likely to develop the disease as someone without a family history of the disease. But experts are quick to point out that the culprit may not lie solely within a person’s genetics: If a family member’s lung cancer was caused by smoking, their relatives may be more likely to smoke themselves or could have been exposed to secondhand smoke too.

Radiation. Exposure to radiation—i.e., energy that’s released in the form of particle or electromagnetic waves— can also increase your risk of lung cancer. Usually this is due to treatment for a previous cancer diagnosis that involved either radiation therapy or imaging tests like CT scans to the chest.

Workplace substances. Working around substances like asbestos (tiny fibers found in the insulation of homes and buildings), arsenic (a poisonous chemical that kills weeds), cadmium (a metallic element used to make batteries and plastics), nickel, tar, and soot can increase your risk of developing lung cancer.


Lung cancer symptoms

Most of the time, people won’t experience any lung cancer symptoms until the advanced stages of the disease. In other instances, doctors can discover the tumor accidentally—during, for example, a routine X-ray or imaging test. The signs of lung cancer are largely the same in both men and women, but when the symptoms do appear, they often overlap with those found in other illnesses. For example, some of the disease’s most common symptoms—including coughing and wheezing—are similar to those of a lingering chest infection.

Coughing. The most common symptom of lung cancer is coughing, which shows up in about 75% of people with the disease, according to a 2014 review published in the journal Surgery. The study authors say that the lung cancer tumor can irritate or squeeze the air passageways that lead into the lungs. Usually, this type of cough either doesn’t go away or gets worse with time.

Chest painIn many cases, chest pain is caused when the lung tumor invades the chest wall, the sides of the cavity that house the heart and lungs. Some people say that the pain feels more intense when they cough, laugh, or take deep breaths.

Coughing up blood. People with lung cancer can cough up streaks of blood from the respiratory tract along with a mix of saliva and mucus, a symptom that’s called hemoptysis. Because the blood is originating from the lungs and throat, it can also contain air, making it appear as if there are bubbles in it.

Difficulty breathing. Called dyspnea, difficulty breathing is another common symptom of lung cancer. The tumor can partially (or completely) obstruct the airways, triggering breathing problems.

Hoarseness. Everyone’s voice sounds different, but people with lung cancer may sound harsher or raspier than usual.

Swelling of the neck and face. If a lung cancer tumor presses on a vein that connects the heart to the head called the superior vena cava, blood can back up, causing the face and neck to appear swollen.

Pneumonia or bronchitis. People with lung cancer can be more likely to have reoccurring chest infections, including pneumonia (which can be caused by bacteria, viruses, or fungi) and bronchitis (usually caused by a virus).

How Is lung cancer diagnosed?

Lung cancers are usually caught after they have already spread to other areas of the body, however there are lung cancer screening tests that can detect the disease in its earlier stages. A large clinical trial found that one test, called a low-dose CT scan (LDCT), was shown to lower the chances of dying from lung cancer in people at high risk for the disease by about 20% compared to chest X-rays. The ACS says that people may be candidates for lung cancer screening if they are over the age of 55, are in fairly good health, have smoked at least a pack of cigarettes a day for 30 years or two packs a day for 15 years, and are either still smoking or have quit within the last 15 years.

Diagnosing lung cancer is largely the same for both types of the disease. Doctors will typically look for abnormal lung growths by using an X-ray; if they spot something suspicious, they may also order a CT scan, which uses many X-rays to show a more detailed image of your chest. Other options include a positron emission tomography (PET) scan, which can determine whether the cancer has spread to the lymph nodes or other organs, and a bone scan, which can show if the cancer has spread to the bones.

After the test results come back, doctors will take a sample from either a person’s lung secretions (for example, phlegm), the fluid area around the lung, or the suspicious area. To get a sample of the suspicious growth, doctors take a biopsy by using a hollow needle that is inserted into the chest wall. The diagnosis is made after the cells are examined for cancerous growths under a microscope.

Types of lung cancer

There are two main types of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), and both are treated in different ways. About 80% to 85% of people who develop lung cancer will develop non-small cell lung cancer, a group that includes adenocarcinoma, squamous cell carcinoma, and large cell carcinomas. These cancers can typically be treated with surgery, chemotherapy, radiation therapy, targeted therapy, immunotherapy, or a combination of these options.

The other 10% to 15% of people with lung cancer will develop small cell lung cancer, an aggressive type of cancer that is treated with chemotherapy and radiation therapy. Small lung cancer grows at a faster rate than the non-small cell kind.

There is also a third type of tumor that’s found in the lungs. While not a “true” lung cancer, metastatic lung cancer is a type of disease that developed in another area of the body—for example, the bladder, colon, or kidneys—before spreading to the lungs.

Adenocarcinomas. About 40% of all lung cancers are adenocarcinomas, according to the ACS. Although it’s mainly seen in people who smoke or used to smoke, it’s also the most common type of lung cancer among those who’ve never used tobacco products. Adenocarcinoma is often found in outer parts of the lungs and tends to grow at a slower rate than other types of lung cancers.

Squamous cell carcinomas. Also called epidermoid carcinoma, this type of cancer begins in the squamous cells, which are located in tissues of the respiratory tract, digestive system, and more. Viewed under a microscope, squamous cells are thin, flat cells that resemble fish scales. About 25% to 35% of all lung cancers are of the squamous cell variety, according to the ACS. Squamous cell carcinomas are often found near a main air passageway leading into the lungs.

Large cell carcinomas. A faster growing type of cancer, large cell carcinomas account for about 10% to 15% of all lung cancers, according to the ACS, and can grow in any part of the lung.

Small cell lung cancer. The most common form of SCLC is small cell carcinoma, which is almost always caused by smoking. All small cell lung cancers tend to be more common in men than women. Oftentimes, these cells first form in the airway passages in the center of the chest before quickly multiplying into large tumors. These cells are very small, but they spread (or metastasize) faster than non-small cell lung cancers. They eventually reach other areas of the body, including the brain and liver.

Combined small cell lung cancer. The combination of a small cell carcinoma with a non-small cell lung cancer, like adenocarcinoma, squamous cell carcinoma, or large cell carcinoma.

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Lung cancer stages

Doctors use “stages” to classify the amount of cancer in a person’s body. The stage of your lung cancer—stage 1, 2, 3, or 4—will help experts determine what type of treatment you should receive and how the cancer may progress.

When deciding how to stage a person’s cancer, doctors usually use the American Joint Committee on Cancer (AJCC) TNM system. The T denotes the size of the main tumor; the N signifies whether the cancer has spread to the nearby lymph nodes (structures that contain immune cells); and the M refers to how far the cancer has metastasized (or spread). Each letter will then be assigned a number, which will further describe the size of the tumor, how far the cancer has spread into the lymph nodes, and whether the cancer has metastasized to other body parts. Higher numbers mean the cancer is more advanced; lower numbers mean the cancer is less advanced. Doctors will take all these factors into account when they determine a person’s lung cancer stage.

Non-small cell lung cancer can be classified into one of the following stages:

Stage 4 Non-Small Cell Lung Cancer. In stage 4 non-small cell lung cancer (IV NSCLC), the cancer has metastasized, or spread to other parts of the body, including the lymph nodes, liver, bones, or brain. The tumor itself may be any size.

The five-year survival rate for this stage of the disease is about 1%, according to the ACS. For people who are in otherwise good health, treatment options include surgery, chemotherapy, radiation therapy, and immunotherapy. While these treatments aren’t likely to cure the cancer, they can help people live longer and help relieve some symptoms.

Stage 3B Non-Small Cell Lung Cancer. In stage 3B non-small cell lung cancer (IIIB NSCLC), the cancer has grown into other parts of the chest or spread to the nearby lymph nodes in the neck or the opposite lung. (Our bodies contain hundreds of lymph nodes, which are small, bean-shaped structures that carry infection-fighting white blood cells.) These cancers can’t be entirely removed by surgery; people who can tolerate it may decide to try chemo and radiation therapy. The five-year survival rate for stage 3B non-small cell lung cancer is about 5%, according to the ACS.

Stage 3A Non-Small Cell Lung Cancer. In stage 3A non-small cell lung cancer (IIIA NSCLC), the cancer hasn’t spread to distant sites in the body, but it may have spread to nearby lymph nodes. In some cases, surgery can be performed first, followed by chemotherapy and radiation. In other instances, treatment starts with chemo and radiation and may be followed by surgery. The five-year survival rate for people with stage 3A non-small cell lung cancer is about 14%.

Stage 2A and 2B Non-Small Cell Lung Cancer. In stage 2A and 2B non-small cell lung cancer (IIA NSCLC and IIB NSCLC), the cancerous cells may have spread to some lymph nodes, but it hasn’t spread to more distant sites. It may be possible to surgically remove the cancer from the lung (or remove the entire lung), and doctors may be able to remove the lymph nodes that are harboring cancerous cells too. After surgery, doctors can check the edges of the tissue specimen for cancer; if any cancerous cells are present (these are called “positive margins”), a second surgery—or chemo or radiation therapy—might also be necessary. Even if doctors don’t find any positive margins, they may still recommend chemotherapy, which can eliminate any cancer cells that may have been left behind. The five-year survival rates for people with both stage 2A and stage 2B non-small cell lung cancers are about 30% and 31% respectively, according to the ACS.

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Stage 1A and 1B Non-Small Cell Lung Cancer. In stage 1A and 1B non-small cell lung cancers (IA NSCLC and IB NSCLC), the cancer is no larger than five centimeters across and hasn’t spread to the lymph nodes or other distant sites in the body. Some people may only need to have surgery to remove the part of the lung that contains the tumor. After the procedure, doctors will look for cancer cells at the edges of the tissue (called “positive margins”). If cancer cells are present, it’s possible that some cancer has been left behind, and that a second surgery—and either chemotherapy or radiation—might also be necessary. For people with stage 1A NSCLC, the five-year survival rate is about 49%; for those with IB NSCLC, the five-year survival rate is about 45%, according to the ACS.

To treat small cell lung cancer, doctors use a two-stage system, classifying these cancers as either “limited” or “extensive.” In most cases, small cell lung cancer has spread to other areas of the body by the time it is diagnosed. According to the NCI, the five-year survival rate for people with this type of cancer is 5% to 10%.

Limited Stage Small Cell Lung Cancer. About one-third of people with SCLC are diagnosed with limited stage disease, in which the cancer is located only on one side of the person’s chest. In these cases, doctors may be able to remove the tumor and nearby lymph nodes. After the procedure, people may also receive chemotherapy and sometimes radiation.

Small cell lung cancer can also spread to a person’s brain; oftentimes, doctors try to prevent this from occurring by giving people low-doses of radiation therapy to the head (called prophylactic cranial irradiation, or PCI).

Extensive Stage Small Cell Lung Cancer. For people with extensive stage SCLC—in which the disease has spread throughout the body—chemotherapy can help shrink the cancer. Although chemo can lessen a person’s symptoms and help them live longer, the cancer almost always returns in the future.

Lung cancer treatments

Different stages of non-small cell lung cancer are treated in different ways. People with early-stage cancers may be treated with surgery; operations include a pneumonectomy (the removal of the entire lung), a lobectomy (the removal of one of the five lobes, or sections, of the lungs), a wedge resection (the removal of part of one lobe), or a sleeve resection (which is performed on the airways in the lungs).

Other lung cancer treatments include chemotherapy, in which an anti-cancer drug is either taken orally or injected into the bloodstream, and radiation therapy, which can kill the cancer cells with high-energy rays (think X-rays, but in stronger doses).

Small cell lung cancer is usually treated with both chemotherapy and radiation at the same time. (Surgery typically isn’t effective for people with small cell lung cancer; the tumor is either too large or the cancer has spread to too many other places in the body for doctors to remove it during an operation.) To prevent the cancer from spreading to the brain—something that, without treatment, can occur in about half of people with this disease—doctors will administer low-doses of radiation therapy to the head, called prophylactic cranial irradiation, or PCI.

If small cell lung cancer has spread throughout the body, chemo is unlikely to cure the disease, but it can shrink the tumor and help people live longer, with fewer symptoms.

Lung cancer survival rates

Although lung cancer can be cured, the disease is currently the most fatal cancer in the United States, responsible for an estimated 155,870 deaths a year, according to the NCI.

A person’s lung cancer prognosis is largely dependent on the disease’s stage at the time of the diagnosis. For example, the five-year survival rate for people with early-stage lung cancer is about 49%, according to the NCI, compared to about 2% for those with more advanced disease.

The five-year survival rate for people with stage 1 non-small cell lung cancer is about 49%, according to the ACS, with the survival rate declining at later stages. Those with stage 2 non-small cell lung cancer have a five-year survival rate of about 30%, those with stage 3A have a 14% five-year survival rate, those with stage 3B have a 5% five-year survival rate, and people with stage 4 have a five-year survival rate of about 1%.

The NCI calls the prognosis for small cell lung cancer “unsatisfactory.” Without treatment, people with this disease may expect to live for about two to four months; the overall five-year survival rate is 5% to 10%. People with lung cancer may be eligible to participate in a clinical trial that is designed to treat their type of cancer.

Lung cancer prevention

Lung cancer is the deadliest type of cancer in the United States. If you’re wondering how to prevent lung cancer, the number one thing you can do is avoid tobacco products. Cigarette smoking is responsible for up to 90% of all lung cancers, and the risk increases for people who smoke more often or who started smoking at a younger age. Even if you currently smoke, quitting will lower your chances of developing lung cancer in the future.

You should also try to steer clear of secondhand smoke as much as possible. Being around others who smoke either at home or at work can increase your risk of developing lung cancer by 20% to 30% compared to people who can avoid cigarette smoke.

Other lung cancer prevention tips include lessening any exposure you might have to harmful substances in the workplace and at home. For example, radon—an odorless, tasteless, invisible gas that can creep into your home through the walls or foundation—accounts for about 30% of the deaths from lung cancer in people who’ve never smoked. The CDC estimates that nearly one in every 15 houses may have high levels of radon, which can only be detected with a specific type of test. You can find a kit from the National Radon Program Services.