Causes | Symptoms | Diagnosis | Types of lung cancer | Stages | Treatment | Survival rates | Prevention
What is lung cancer?
Lung cancer is a condition that causes cells to divide in the lungs uncontrollably. This causes the growth of tumors that reduce a person’s ability to breathe. 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.
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
Symptoms of non-small cell lung cancer and small cell lung cancer are basically the same.
Early symptoms may include:
- lingering or worsening cough
- coughing up phlegm or blood
- chest pain that worsens when you breathe deeply, laugh, or cough
- shortness of breath
- weakness and fatigue
- loss of appetite and weight loss
You might also have recurrent respiratory infections such as pneumonia or bronchitis.
As cancer spreads, additional symptoms depend on where new tumors form. For example, if in the:
- lymph nodes: lumps, particularly in the neck or collarbone
- bones: bone pain, particularly in the back, ribs, or hips
- brain or spine: headache, dizziness, balance issues, or numbness in arms or legs
- liver: yellowing of skin and eyes (jaundice)
Tumors at the top of the lungs can affect facial nerves, leading to drooping of one eyelid, small pupil, or lack of perspiration on one side of the face. Together, these symptoms are called Horner syndrome. It can also cause shoulder pain.
Tumors can press on the large vein that transports blood between the head, arms, and heart. This can cause swelling of the face, neck, upper chest, and arms.
Lung cancer sometimes creates a substance similar to hormones, causing a wide variety of symptoms called paraneoplastic syndrome, which include:
- muscle weakness
- fluid retention
- high blood pressure
- high blood sugar
How Is lung cancer diagnosed?
If a doctor identifies a suspicious lesion on a lung cancer screening, or a person is experiencing symptoms that could indicate lung cancer, several diagnostic tests are available to confirm the next steps.
Examples of these include:
Imaging studies: Computed tomography (CT) and positron emission tomography (PET) scans might reveal areas of lung tissue with cancer. Bone scans can also indicate cancerous growths. Doctors may also use these scans to track the progress of treatment or to ensure cancer has not returned, following a course of treatment.
Tissue sampling: If a doctor identifies a suspicious lesion on an imaging study, they may recommend taking a sample of lung tissue to test for potentially cancerous cells.
There are different ways to take a tissue sample, and the method often depends on the location of the lesion.
One example is when a doctor performs a bronchoscopy, which involves inserting a special thin, lighted scope with a camera on the end. This helps the doctor to see the lesion and then to obtain samples.
Less accessible lesions in the lungs may require a more invasive surgical procedure to remove lung tissue, such as thoracoscopy or video-assisted thoracic surgery.
Lab testing: A doctor may also order sputum testing or blood testing to check for the presence of lung cancer.
A doctor will use this information to determine what type of lung cancer may be present, and how advanced the disease has become.
The importance of early diagnosis
Early diagnosis of lung cancer can be lifesaving. This is because lung cancer cells can travel to other areas of the body before a doctor detects them in the lungs. If this spread or metastasis has taken place, it makes treating the disease much more difficult.
Sometimes, a doctor will recommend a person have lung cancer screenings. These are performed using a low-dose CT scanner. Not everyone is a candidate for this screening, but it can help doctors identify lung cancer earlier in some individuals.
According to the American Lung Association, people who may be candidates for lung cancer screenings are those who:
- are between 55 and 80 years of age
- are a 30 pack-year history of smoking, meaning they smoked one pack per day for 30 years or two packs per day for 15 years
- are a current smoker or smoker who has quit within the past 15 years
Insurance will often cover this screening if a person meets all these criteria. However, people should always check with their insurance company before signing up for lung cancer screening.
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.
Lung cancer stages
The staging of cancer indicates how far it has spread through the body and its severity. This classification helps clinicians support and direct treatment for the best results.
Each stage determines whether cancer has or has not spread or has spread to nearby lymph nodes. It may also take into account the number and size of the tumors.
The lymph nodes are part of the lymphatic system, which connects to the rest of the body. If cancer reaches these, it can metastasize, or spread further, becoming more dangerous.
Staging for lung cancer is extremely complex and extensive with several sub-groups within each stage.
Initially, clinicians divide it into small cell and non-small cell classifications.
Staging definitions may vary, but doctors typically stage non-small cell lung cancer using the tumor size and the spread to guide them in the following way:
- Occult, or hidden: Cancer does not show on imaging scans, but cancerous cells might appear in the phlegm or mucus and may have reached other parts of the body.
- Stage 0: The doctor finds abnormal cells only in the top layers of cells lining the airways.
- Stage I: A tumor has developed in the lung, but is under 5 centimeters (cm) and has not spread to other parts of the body.
- Stage II: The tumor is smaller than 5 cm and might have spread to the lymph nodes in the area of the lung, or smaller than 7 cm and spread to nearby tissues but not lymph nodes.
- Stage III: Cancer has spread to the lymph nodes and reached other parts of the lung and surrounding area.
- Stage IV: Cancer has spread to distant body parts, such as the bones or brain.
Small cell lung cancer has its own categories, limited and extensive, referring to whether cancer has spread within or outside the lungs.
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Lung cancer treatments
It’s usually a good idea to seek a second opinion before beginning treatment. Your doctor may be able to help make that happen. If you’re diagnosed with lung cancer, your care will likely be managed by a team of doctors who may include:
- a surgeon who specializes in the chest and lungs (thoracic surgeon)
- a lung specialist (pulmonologist)
- a medical oncologist
- a radiation oncologist
Discuss all your treatment options before making a decision. Your doctors will coordinate care and keep each other informed.
Treatment for non-small cell lung cancer (NSCLC) varies from person to person. Much depends on specific details of your health.
Stage 1 NSCLC: Surgery to remove a portion of the lung may be all you need. Chemotherapy may also be recommended, especially if you’re at high risk of recurrence.
Stage 2 NSCLC: You may need surgery to remove part or all of your lung. Chemotherapy is usually recommended.
Stage 3 NSCLC: You may require a combination of chemotherapy, surgery, and radiation treatment.
Stage 4 NSCLC is particularly hard to cure. Options include surgery, radiation, chemotherapy, targeted therapy, and immunotherapy.
Options for small cell-lung cancer (NSCLC) also include surgery, chemotherapy, and radiation therapy. In most cases, the cancer will be too advanced for surgery.
Clinical trials provide access to promising new treatments. Ask your doctor if you’re eligible for a clinical trial.
Some people with advanced lung cancer choose not to continue with treatment. You can still choose palliative care treatments, which are focused on treating the symptoms of cancer rather than the cancer itself.
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.