What Is Lung Cancer? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Lung cancer is a form of cancer — an out-of-control growth of abnormal cells — that typically starts in the cells lining the bronchi (tubes that move air into and out of the lungs) or other parts of the lungs, according to the American Cancer Society. (1)

Lung cancer is by far the leading reason men and women die from cancer in the United States, according to the National Cancer Institute, which estimates that the disease accounts for around 25 percent of cancer-related fatalities. (2)

Types of Lung Cancer

There are two main types of lung cancer:

• Non-small-cell lung cancer
• Small-cell lung cancer

Types of Non-Small-Cell Lung Cancer

From 80 to 85 percent of people with lung cancer have non-small-cell lung cancer (NSCLC), according to the American Cancer Society. (1)

There are three main forms of NSCLC, according to the National Institutes of Health: (3)

• Adenocarcinomas The most common form of NSCLC, often found in an outer area of a lung
• Squamous-Cell Carcinomas Usually found in the center of a lung next to a bronchus
• Large-Cell Carcinomas Can be located anywhere in the lung

Types of Small-Cell Lung Cancer

Small-cell lung cancer (SCLC) accounts for around 10 to 15 percent of all lung cancers in the United States, according to the American Cancer Society. (1)

Small-cell lung cancer tends to be more aggressive than non-small-cell lung cancer, according to LungCancer.org. (4)

Learn More About Types of Lung Cancer

Learn More About Non-Small-Cell Lung Cancer

After doctors have diagnosed lung cancer and identified the type, the next step is staging — ascertaining the size and extent of the tumor and determining whether the cancer has spread and, if so, how far.

Staging is an important part of determining treatment. Different types of lung cancer are staged differently.

Main Stages of Non-Small-Cell Lung Cancer (NSCLC)

NSCLC may proceed from stage 0 to stage 4 lung cancer, with many substages. In general, the higher the number, the more advanced the disease.

The breakdown here simplifies the criteria: (5,6)

• Stage 0 The cancer is very small and hasn’t spread beyond the inner lining of the lungs. It’s sometimes known as “carcinoma in situ.”
• Stage 1 The cancer is only located in the lungs and hasn’t spread to any lymph nodes. The tumor is usually smaller than 4 centimeters (cm) across — about 1.5 inches.
• Stage 2 The cancer is larger than 4 cm or has spread to nearby lymph nodes, the chest wall, the lining of the lungs, or the diaphragm.
• Stage 3 The cancer is larger than 7 cm (about 3 inches) or it has grown large and spread to nearby tissues or further into the lymph nodes in the middle of the chest.
• Stage 4 The cancer has spread to both lungs, to fluid surrounding the lung or the heart, or to more distant sites in the body, such as the brain, bones, and liver.

Main Stages of Small-Cell Lung Cancer (SCLC)

Small-cell lung cancer is generally divided into two stages, according to the American Cancer Society: (7)

• Limited Stage The cancer is only on one side of the chest. If lymph nodes are affected, they also are typically on that side of the chest.
• Extensive Stage The cancer has spread widely throughout the lung, to the other lung, to lymph nodes on both sides of the chest, or to other parts of the body. The majority of people with SCLC have extensive disease when diagnosed.

Learn More About the Stages of Lung Cancer

Signs of lung cancer don’t typically appear until the disease is advanced. Lung cancer symptoms include, according to the Mayo Clinic:

• A new cough that doesn’t go away
• Coughing up blood, even a small amount
• Shortness of breath
• Chest pain
• Hoarseness
• Losing weight without trying
• Bone pain
• Headache (8)

Is Back Pain a Symptom of Lung Cancer?

There are many reason for back pain including, rarely, cancer. Around 1 in 4 people with lung cancer say they have experienced back pain at some point.

The pain may come from a tumor pressing on the spine or affecting nerves around the chest wall and spine. Lung cancer that has metastasized to the spine may also cause back pain, notes the Dana-Farber Cancer Institute. (9)

Read More About Lung Cancer Symptoms

Tobacco smoking is the number one risk factor for lung cancer. The National Cancer Institute says that tobacco smoking causes about 9 out of 10 cases of lung cancer in men and roughly 8 out of 10 cases of lung cancer in women. (10)

Cigar smoking and pipe smoking are almost as likely to cause cancer as cigarette smoking, according to the American Cancer Society. (11)

According to the Centers for Disease Control and Prevention (CDC), other factors that raise lung cancer risk include: (12)

• Environmental risk factors, such as exposure to the gas radon
• Secondhand cigarette smoke or other tobacco smoke
• Family history of lung cancer
• Radiation to the chest as a treatment for other cancers
• Exposure to substances in the workplace such as asbestos

Learn More About Causes and Risk Factors for Lung Cancer

Lung Cancer and Smoking

According to the CDC, cigarette smoking is linked to anywhere from 80 to 90 percent of lung cancer deaths.

People who smoke are 15 to 30 times more likely to get lung cancer or die from it than people who have never smoked. 

Quitting smoking at any age can lower the risk of developing lung cancer. (12)

Secondhand Smoke and Lung Cancer

Secondhand smoke is smoke that comes from a burning cigarette or other tobacco product, or that is exhaled by a person who is smoking. Both can lead to lung cancer.

According to the CDC, secondhand smoke causes more than 7,300 deaths among U.S. nonsmokers each year.

The CDC also states that there is no risk-free level of exposure to secondhand smoke. (13)

Marijuana and Lung Cancer

There’s no evidence that smoking marijuana raises lung-cancer risk, but there’s reason to believe it may. Marijuana smoke contains tar and several other cancer-causing substances that are found in tobacco smoke.

Since marijuana is illegal in many places in the United States, researchers face challenges in studying its health effects.

And since studies of lung cancer and marijuana have often found that many marijuana smokers also smoke cigarettes, it's hard to know how much each contributes to lung cancer risk. (11)

A Swedish study that followed nearly 50,000 men over a 40-year period found a link between marijuana use and lung cancer. Heavy marijuana smokers — those who reported smoking more than 50 times in their life — were twice as likely to get lung cancer as those who didn't smoke marijuana. (14)

E-Cigarettes and Lung Cancer

E-cigarettes, a type of electronic nicotine delivery system, are still fairly new and more research is needed to know whether their long-term use (known as vaping) poses a lung cancer risk. (11)

Lung cancer survival rates typically reveal the percentage of people with the same type and stage of cancer who are still alive five years after diagnosis.

A five-year survival rate of 61 percent, for instance, means that 61 percent of people with a particular type and stage of lung cancer are still alive five years after diagnosis.

These numbers are estimates that don’t account for many other factors influencing the course of the disease, and they can’t predict how long any one person with lung cancer can expect to live.

The most recent data, compiled by the National Cancer Institute from its SEER (Surveillance, Epidemiology, and End Results) study, is 5 to 10 years old — meaning it doesn’t account for advances in lung cancer treatment, which have been significant since 2015.

Instead of employing the most widely used type of staging, which ranges from stage 0 to stage 4, the SEER data relies on the following terms:

• Localized The cancer has not spread outside the lung.

• Regional The cancer has spread outside the lung to nearby structures or lymph nodes.

• Distant The cancer has spread to more distant parts of the body, such as the bones, the liver, or the other lung.

According to the American Cancer Society, the survival rates for these categories are: (16)

Non-Small-Cell Lung Cancer

• Localized Five-year relative survival rate is 61 percent.

• Regional Five-year relative survival rate is 35 percent.

• Distant Five-year relative survival rate is 6 percent.

Small-Cell Lung Cancer

• Localized Five-year relative survival rate is 27 percent.

• Regional Five-year relative survival rate is 16 percent.

• Distant Five-year relative survival rate is 3 percent.

Home remedies and homeopathic medicine will not cure lung cancer, but according to the Mayo Clinic, certain alternative and complementary therapies may make it easier to cope with symptoms of the disease or side effects of treatment, including: (20)

• Acupuncture
• Aromatherapy
• Massage
• Music Therapy
• Yoga
  

Palliative care can also make life with cancer better. Some examples include:

• Emotional support and counseling
• Nutritional supplements
• Medication to treat pain, per the American Lung Association (21)
• Medical procedures to make breathing easier, per the American Cancer Society (22)

Learn More About Lung Cancer Alternative and Complementary Therapies, and Palliative Care

Prevention of Lung Cancer

There’s no way to completely eliminate lung cancer risk, but you can lower the odds. A few things you can do:

• Don’t smoke, or if you do smoke, stop
• Avoid secondhand smoke
• Test your home for radon
• Avoid carcinogens at work, like asbestos
• Eat a diet loaded with fruits and vegetables
• Exercise most days of the week (8)

Learn More About Lung Cancer Prevention

Lung cancer can lead to a variety of complications, including:

• Pain You may feel pain if cancer spreads (metastasizes) to the lung lining, the bone, or another area of the body.
• Shortness of Breath This can occur if the cancer grows to block the major airways or if fluid builds up around the lungs, making it harder to take a full breath.
• Coughing Up Blood A tumor can cause bleeding in the airway. (8)

Learn More About Lung Cancer Complications

A number of other diseases and chronic health conditions appear to increase the risk of developing lung cancer.

These include:

• Previous Lung Disease According to the Mayo Clinic, researchers have found an association between lung cancer and a history of other lung diseases, such as chronic obstructive pulmonary disease (COPD). (25)
• HIV People infected with human immunodeficiency virus (HIV) are twice as likely to develop lung cancer as the general population, per the National Cancer Institute. (26)

If you or someone close to you receives a lung cancer diagnosis, there are many resources for information and support, including:

• American Cancer Society The American Cancer Society operates a National Cancer Information Center where trained specialists are available 24 hours a day, 365 days a year, via phone or live chat.
• National Cancer Institute The National Cancer Institute is a go-to source for reliable information about cancer topics, research, and clinical trials.
• CancerCare CancerCare is a nonprofit that supplies free, professional support services for people with lung cancer, treatment information, and lung cancer support groups led by oncology social workers.

Additional reporting by Pamela Kaufman.