Lung health
Lung Cancer: Symptoms, Risk Factors and Screening Explained
Lung cancer can sometimes develop without causing any symptoms. Understanding your risk — and knowing when CT screening may be appropriate — can help cancers be detected earlier.
Consultant Radiologist8–10 min readReviewed: September 2026
Lung cancer is one of the most important cancers to diagnose early.
One of the challenges is that early lung cancer may cause no symptoms at all. A small cancer can be growing within the lung while someone continues to feel completely well.
This is one reason why CT scanning has become so important in detecting lung cancer earlier, particularly in people who are at higher risk.
What is lung cancer?
Lung cancer develops when abnormal cells within the lung begin to grow in an uncontrolled way. Broadly, it is divided into two main types.
Non-small cell lung cancer
Approximately 85% of lung cancers.
Includes adenocarcinoma and squamous cell carcinoma, among other subtypes.
Small cell lung cancer
Approximately 15% of lung cancers.
Tends to grow and spread more rapidly, and is treated differently.
Lung cancer is not one single disease. Treatment depends on the cancer type, stage and increasingly its molecular characteristics.
What increases your risk?
Most important factor
Smoking
Smoking is by far the most important preventable risk factor for lung cancer.
Risk generally increases with the number of cigarettes smoked, the number of years someone has smoked and their total lifetime tobacco exposure.
Stopping smoking is beneficial even after many years of smoking.
What is a pack-year?
One pack-year is approximately equivalent to smoking 20 cigarettes per day for one year. For example, 10 cigarettes per day for 20 years is approximately 10 pack-years.
Passive smoking
Regular exposure to tobacco smoke from other people can also increase lung cancer risk.
Radon
A naturally occurring radioactive gas that can accumulate in buildings. Long-term exposure is associated with lung cancer.
Occupational exposure
Examples include asbestos, silica, diesel exhaust, arsenic, chromium and nickel.
Air pollution
Long-term exposure to fine particulate air pollution is associated with increased lung cancer risk.
Previous lung disease
Conditions such as COPD, emphysema and pulmonary fibrosis are associated with higher risk.
Age
Risk increases with age.
Family history
Having a close relative with lung cancer can be associated with increased risk.
Can you develop lung cancer if you have never smoked?
Yes.
Although smoking is the dominant risk factor, lung cancer also occurs in people who have never smoked.
Possible contributing factors
- Passive smoking
- Radon
- Air pollution
- Occupational exposures
- Inherited susceptibility
Do not ignore concerning symptoms simply because you have never smoked.
What symptoms should you look out for?
Early lung cancer may cause no symptoms.
Persistent cough
A cough that does not settle or continues for several weeks.
A change in your usual cough
A longstanding cough becoming more frequent, severe or different.
Coughing up blood
Even small amounts of unexplained blood in sputum should be assessed.
Breathlessness
New or worsening unexplained shortness of breath.
Chest or shoulder pain
Persistent unexplained discomfort can occasionally occur.
Recurrent chest infections
Particularly infections repeatedly affecting the same area of the lung.
Unexplained weight loss
Loss of appetite
Persistent fatigue
Persistent hoarse voice
Less common symptoms
- Persistent bone pain
- Headaches
- Neurological symptoms
- Enlarged lymph nodes
Having one of these symptoms does not mean you have lung cancer. Many are caused by much more common conditions. Persistent or unexplained symptoms should nevertheless be assessed.
When should I speak to my GP?
- A cough that does not go away
- A change in your usual cough
- Coughing up blood
- Worsening breathlessness
- Unexplained weight loss
- Persistent chest discomfort
- Recurrent chest infections
Do not wait for a lung cancer screening invitation if you already have symptoms. Screening is primarily designed for people who do not have symptoms.
Significant coughing up of blood, severe breathing difficulty or suddenly becoming very unwell requires more urgent medical assessment.
Who is NHS lung cancer screening for?
England is rolling out a national NHS Lung Cancer Screening Programme, developed from the Targeted Lung Health Check programme.
- 1Age 55–74
- 2Current or former smoker
- 3Invited for a lung health assessment
- 4Individual lung cancer risk calculated
- 5People above the programme's risk threshold may be offered low-dose CT
Important
Being aged 55–74 and having ever smoked does not automatically mean you will receive a CT scan.
Your smoking history and other health information are used to calculate your individual risk of developing lung cancer. Those whose calculated risk is sufficiently high may be offered a low-dose CT scan.
The programme is continuing to roll out across England, so availability and timing vary between areas.
Why don't we screen everyone?
CT is extremely sensitive. This allows radiologists to detect very small abnormalities, but many of the abnormalities detected are not cancer.
Possible consequences of widespread unnecessary screening
- Unnecessary repeat CT scans
- Anxiety
- PET-CT examinations
- Biopsies
- Procedural complications
- Radiation exposure
- Overdiagnosis
Screening is therefore targeted towards people whose probability of lung cancer is high enough that the expected benefits outweigh the potential harms.
What is a low-dose CT?
A low-dose CT, often shortened to LDCT, uses X-rays to create detailed cross-sectional images of the lungs while deliberately using less radiation than many standard diagnostic CT examinations.
The actual image acquisition usually takes only seconds.
Why is CT used for lung cancer screening?
CT can identify abnormalities that are substantially smaller or more subtle than those visible on a conventional chest X-ray. That matters when the aim is to find a cancer before it causes symptoms.
The evidence
Large randomised trials including the National Lung Screening Trial and NELSON trial demonstrated that low-dose CT screening can reduce deaths from lung cancer in appropriately selected high-risk populations.[6,7]
What does a radiologist look for on a lung CT?
One of the main abnormalities radiologists look for is a lung nodule.
What is a lung nodule?
A lung nodule is a small rounded or irregular area within the lung.
Most lung nodules are not cancer.
What is assessed
- Size
- Shape
- Margins
- Location
- Whether it is solid, part-solid or ground-glass
- Whether there are multiple nodules
- Whether it has changed compared with previous scans
- How quickly it is growing
Change over time can be one of the most important clues.
What happens if a nodule is found?
Lower-risk nodule
Often monitored, or may require no immediate action.
Intermediate nodule
May require another CT at an appropriate interval to assess for change.
More suspicious nodule
May lead to:
- Diagnostic CT
- PET-CT
- Specialist lung multidisciplinary team review
- Bronchoscopy
- CT-guided biopsy
- Another form of tissue sampling
Not every suspicious lung nodule should be biopsied immediately.
Decisions depend on:
- Size
- Appearance
- Location
- Cancer probability
- Growth
- Patient health
- Whether biopsy can be performed safely
What is a PET-CT scan?
CT
Shows the anatomy — where an abnormality is and what it looks like.
PET
Provides information about metabolic activity.
The most commonly used PET tracer in lung cancer is 18F-FDG, a radioactive form of glucose.
PET-CT can help assess:
- The lung lesion
- Lymph nodes
- Possible spread elsewhere in the body
- Overall cancer stage
PET-CT is not a cancer detector on its own. Infection and inflammation can also show increased FDG uptake, while some cancers show relatively little uptake.
Finding lung cancer earlier can change the treatment options
75%+
More than three quarters of lung cancers detected through the NHS England programme to March 2025 were diagnosed at Stage I or Stage II.[8]
63.1%
Stage I
12.6%
Stage II
The purpose of screening is not simply to find more cancers. It is to find cancers at an earlier stage, when potentially curative treatment may be more achievable.
Can I reduce my risk of lung cancer?
Don't smoke
Avoiding tobacco is the most effective way to reduce lung cancer risk.
Stop smoking
Stopping remains beneficial regardless of how long someone has smoked.
Reduce occupational exposure
Follow appropriate workplace protection around substances such as asbestos and silica.
Be aware of radon
Testing and mitigation can reduce exposure in areas with elevated indoor radon levels.
The key message
Lung cancer does not always announce itself with dramatic symptoms.
Sometimes it begins as a tiny abnormality on a CT scan in someone who feels completely well.
That is why understanding risk matters.
If you are invited for NHS lung cancer screening, attending the assessment could potentially allow a cancer to be detected at a much earlier stage.
And whether or not you are eligible for screening, persistent symptoms such as a changing cough, coughing up blood, unexplained weight loss or worsening breathlessness should not simply be ignored.
About the author
Dr Prashant Bamania
Consultant Radiologist · Founder & Host, Live, Onward
Dr Prashant Bamania is a Consultant Radiologist with subspecialist interests in cardiothoracic and musculoskeletal imaging.
Through Live, Onward, he explains medical imaging and health conditions in clear, accessible language to help people better understand what happens inside the body.
Understand the scan. Understand the condition.
Live, Onward brings together medical expertise, visual explanation and the experiences of people who have actually lived through major health conditions.
Discover Live, OnwardMedical references(show)
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- 7.de Koning HJ, van der Aalst CM, de Jong PA, et al. Reduced Lung-Cancer Mortality with Volume CT Screening in a Randomized Trial. N Engl J Med. 2020;382(6):503-513. PMID: 31995683
- 8.Implementation of the NHS England Lung Cancer Screening Programme over 5 years. 2026. PMID: 41872602