Lung Cancer: Causes, Symptoms, Stages, Screening and Outlook

Lung Cancer: Causes, Symptoms, Stages, Screening and Outlook

Lung cancer is cancer that starts in the cells of the lungs, and cigarette smoking is linked to about 80% of lung cancer deaths in the United States. It often causes no symptoms until it's advanced, which is why yearly low-dose CT screening is recommended for many adults aged 50 to 80 with a heavy smoking history.

This guide is for anyone worried about symptoms, deciding whether to get screened, or trying to understand a new diagnosis in themselves or someone close to them.

Key takeaways

  • People who smoke cigarettes are 15 to 30 times more likely to get or die from lung cancer than people who don't smoke, according to the CDC.
  • Non-small cell lung cancer makes up about 80% to 85% of lung cancers; small cell lung cancer makes up about 10% to 15%.
  • The US Preventive Services Task Force recommends yearly low-dose CT screening for adults aged 50 to 80 with a 20 pack-year smoking history who smoke now or quit within the past 15 years.
  • The five-year relative survival rate is 65.5% when lung cancer is found while still localized, compared with 10.5% after it has spread to distant organs.
  • Radon, secondhand smoke, air pollution and some workplace exposures cause lung cancer in people who have never smoked.

What causes lung cancer?

Smoking causes most lung cancer, but it isn't the only cause. Radon gas, secondhand smoke, workplace chemicals, air pollution and family history also raise risk, and some people with lung cancer never smoked.

The CDC's list of lung cancer risk factors includes:

  • Cigarette smoking, the leading risk factor. Cigars and pipes also raise risk. Tobacco smoke contains more than 7,000 chemicals, and at least 70 are known to cause cancer.
  • Secondhand smoke from other people's cigarettes, pipes or cigars.
  • Radon, a natural radioactive gas that can build up indoors. It causes lung cancer in people who have never smoked and raises risk further in people who do.
  • Workplace exposures such as asbestos, arsenic, diesel exhaust, some forms of silica and some forms of chromium.
  • Air pollution.
  • Personal or family history of lung cancer.
  • HIV infection and previous radiation to the chest.
  • Beta carotene supplements, especially in people who smoke heavily or drink daily. Beta carotene from food doesn't raise risk.
  • Arsenic or radon in well water.

Diet research is still developing; our look at processed meat, nitrites and lung function covers one area being studied. Quitting smoking remains the most effective single step at any age, and if you've tried before, our guide on whether cravings ever go away explains what long-term recovery looks like.

What are the early symptoms of lung cancer?

Early lung cancer usually has no symptoms. When symptoms appear, the most common are a cough that won't go away or gets worse, chest pain, shortness of breath, and coughing up blood.

The CDC lists these possible symptoms:

  • A cough that gets worse or doesn't go away
  • Chest pain
  • Shortness of breath
  • Wheezing
  • Coughing up blood
  • Feeling very tired all the time
  • Weight loss with no known cause

Repeated bouts of pneumonia and swollen lymph nodes in the chest can also occur. All of these can have other causes, from infections to heart problems. Chest discomfort, for example, has many sources, as our article on chest pain during strong emotions explains. Symptoms that linger, like a cough or fatigue that hangs on after a virus, are worth checking; see our guide to persistent flu-like symptoms for how doctors work these up.

What are the types and stages of lung cancer?

There are two main types: non-small cell lung cancer (NSCLC), which is far more common, and small cell lung cancer (SCLC), which tends to grow faster. Stage describes how far the cancer has spread and guides treatment.

Types

The American Cancer Society says about 80% to 85% of lung cancers are NSCLC and about 10% to 15% are SCLC.

TypeShare of lung cancersKey features
Non-small cell (NSCLC): adenocarcinomaMost common NSCLC subtypeThe type most often found overall
NSCLC: squamous cell carcinomaPart of the 80% to 85%Starts in flat cells lining the airways; often linked to smoking; usually near a main airway
NSCLC: large cell carcinomaPart of the 80% to 85%Can appear anywhere in the lung; tends to grow and spread quickly
Small cell (SCLC)About 10% to 15%Treated differently from NSCLC
Carcinoid tumorsFewer than 5% of lung tumorsMost grow slowly

Stages

Doctors use a detailed numbered system, from stage 0 and I (small and confined to the lung) up to stage IV (spread to distant organs). For statistics, the National Cancer Institute groups lung cancer into three broader summary stages:

  • Localized: still only in the lung
  • Regional: spread to nearby lymph nodes or tissues
  • Distant: spread to other parts of the body, such as the other lung, bones, brain or liver

Small cell lung cancer is also often described as limited (one side of the chest) or extensive (more widespread). Your care team will explain exactly which system applies to you.

Who should get screened for lung cancer?

Yearly low-dose CT screening is recommended for adults aged 50 to 80 who have a 20 pack-year smoking history and still smoke or quit within the past 15 years. Screening finds cancer earlier, when it's more treatable.

A pack-year is a way to measure lifetime smoking: one pack-year equals smoking an average of 20 cigarettes (one pack) a day for a year. Two packs a day for 10 years is 20 pack-years, as is one pack a day for 20 years. Low-dose CT (LDCT) is a quick chest scan that uses a lower radiation dose than a standard CT.

The USPSTF recommendation says to stop screening once someone has gone 15 years without smoking, or if a health problem substantially limits life expectancy or their ability or willingness to have lung surgery. The American Cancer Society guideline also covers ages 50 to 80 with at least 20 pack-years, but it does not set a cutoff for years since quitting, so more former smokers qualify.

Screening eligibility checklist

  1. Are you between 50 and 80 years old?
  2. Add up your pack-years: packs per day multiplied by years smoked. Is it 20 or more?
  3. Do you smoke now, or did you quit within the last 15 years? (Under the ACS guideline, a longer gap may still qualify.)
  4. Are you well enough to have treatment, including surgery, if something is found?
  5. If you answered yes, ask your doctor about a shared decision-making visit to discuss benefits, false alarms and follow-up scans.

Waiting for scan results can be stressful; our practical strategies to calm nerves can help in the days between the scan and the call.

What is the survival outlook for lung cancer?

Outlook depends heavily on stage at diagnosis. Overall, about 29.5% of people are alive five years after diagnosis, but the figure is far higher when cancer is found early.

Figures from the National Cancer Institute's SEER program for 2016 to 2022 show:

Stage at diagnosisShare of casesFive-year relative survival
Localized24%65.5%
Regional21%38.2%
Distant51%10.5%
Unknown4%17.5%
All stages100%29.5%

Five-year relative survival compares people with lung cancer to similar people without it. A 65.5% figure means people with localized lung cancer are, on average, 65.5% as likely as similar people in the general population to be alive five years later. These numbers come from people diagnosed years ago, so they don't reflect the newest treatments, and they can't predict any one person's outcome. SEER estimates 229,410 new US cases and 124,990 deaths in 2026, with a median age at diagnosis of 71.

Notice that about half of cases are found after the cancer has spread. That's the strongest argument for screening eligible people. Be wary of online claims about miracle cures; our guide to how health misinformation spreads shows how to check what you read.

Common mistakes

  • Assuming non-smokers can't get it. Radon, secondhand smoke and air pollution all cause lung cancer in people who never smoked.
  • Brushing off a lingering cough. A "smoker's cough" that changes or won't go away deserves a check.
  • Thinking it's too late to quit. Quitting at any point lowers your future risk and is part of the screening stop rule.
  • Skipping screening for fear of the result. Finding cancer at the localized stage changes the outlook dramatically.
  • Taking beta carotene supplements if you smoke. The CDC notes these raise lung cancer risk in heavy smokers.
  • Not testing for radon. You can't see it, so a home test is the only way to know your level.

When to see a doctor

Call emergency services if you cough up more than a small amount of blood, have severe trouble breathing, or have sudden chest pain. Book a prompt appointment if you have:

  • A cough that won't go away, or a long-standing cough that changes
  • Any blood in your sputum
  • Shortness of breath or wheezing that's new or worsening
  • Chest, shoulder or back pain that doesn't go away
  • Repeated chest infections or pneumonia
  • Unexplained weight loss, loss of appetite or constant tiredness

Also see your doctor if you meet the screening criteria above and haven't been screened.

FAQ

Can you get lung cancer if you've never smoked?

Yes. The CDC lists radon, secondhand smoke, air pollution, workplace exposures such as asbestos and diesel exhaust, family history and previous chest radiation as causes or risk factors. Radon is a particular concern because it can build up indoors without you knowing. Testing your home is a simple way to reduce one of the main non-smoking risks.

How long can you live with lung cancer?

It depends mostly on the stage at diagnosis, the type, your overall health and how the cancer responds to treatment. SEER data show 65.5% five-year relative survival for localized lung cancer and 10.5% once it has spread to distant organs. These are averages from past years and can't predict any individual's outcome.

Is a chest X-ray enough to screen for lung cancer?

No. The recommended screening test is a yearly low-dose CT scan, not a chest X-ray. If you qualify by age and smoking history, ask your doctor about LDCT screening and what follow-up would look like if a spot is found.

What's the difference between small cell and non-small cell lung cancer?

Non-small cell lung cancer accounts for about 80% to 85% of cases and includes adenocarcinoma, squamous cell and large cell carcinoma. Small cell lung cancer accounts for about 10% to 15% and is treated differently. A biopsy tells doctors which type you have.

What to do next

  • Work out your pack-years and check whether you meet the screening criteria.
  • If you smoke, set a quit date and ask your doctor about medicines and support.
  • Test your home for radon, especially if you live on a ground floor or basement level.
  • Book an appointment for any symptom on the list above that's lasted more than a few weeks, and build habits from our list of healthy living basics.

This article is for general information and is not medical advice.

Sources

Last reviewed: October 2026.

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