Lung cancer: symptoms, causes, tests and treatment, a review

Lung cancer is a cancer that starts in the lungs. People with early lung cancer may feel well, so knowing the warning signs and the main risk factors is useful. This article explains what lung cancer is, what raises the risk, how it is found and how it is treated, using information from the World Health Organization (WHO), the NHS and the US National Cancer Institute.

1. Introduction

Lung cancer is cancer found in the lungs. It happens when cells in the lung change and grow in an uncontrolled way, forming a growth called a tumour. The WHO describes it as the leading cause of cancer cases and cancer deaths worldwide, with about 2.5 million new cases and 1.8 million deaths estimated in 2022 ^[1].

There are two main types. Non-small cell lung cancer is the most common, making up about 85% of cases. Small cell lung cancer is less common but typically more aggressive ^[1]. Both types are named by the National Cancer Institute ^[6]. The type matters because it affects which treatments are suitable.

A key problem is late diagnosis. The WHO notes that lung cancer is often found at an advanced stage, when there are fewer treatment options ^[1].

2. Causes and risk factors

The exact cause is often unclear, and the NHS says it may be linked to lifestyle, changes in genes and the environment ^[3]. Some risk factors are well known:

• Smoking. Smoking is the main risk factor. The WHO says tobacco smoking, including cigarettes, cigars and pipes, is behind most preventable lung cancer ^[1]. The National Cancer Institute adds that people who have never smoked can also develop lung cancer ^[6].
• Secondhand smoke. Long-term exposure to other people's smoke raises risk ^{[1, 3]}.
• Air pollution. Both outdoor and indoor household air pollution contribute ^{[1, 3]}.
• Work and home exposures. These include asbestos fibres, which are linked to work in the building industry, as well as silica, diesel exhaust and radon. Radon is a natural gas that can build up inside buildings ^{[1, 3]}.
• Lung disease and family history. Chronic obstructive pulmonary disease (COPD, a long-term lung condition that makes breathing difficult) and having a close relative with lung cancer can raise risk ^[3].

3. Signs and symptoms

Some people have no symptoms in the early stages ^[2]. When symptoms do appear, the NHS lists these main ones ^[2]:

• A cough that does not go away
• Breathlessness
• Coughing up blood
• Pain in the chest or shoulder
• Chest infections that keep coming back or do not clear up
• Weight loss without trying, and reduced appetite
• Ongoing tiredness

Less common signs include swelling of the face or neck, difficulty swallowing, a hoarse voice that lasts, and fingertips that look wider than usual or curve downwards, which is called clubbing ^[2]. The WHO points out that early symptoms can be mild or be mistaken for common breathing problems, which can delay diagnosis ^[1]. The NHS notes that some of these symptoms are very common and can be caused by other conditions, but it is important to get them checked ^[2].

4. Diagnosis and tests

At a first visit, the doctor will usually ask about your symptoms, general health and family history, may listen to your chest, and may arrange a blood test or a chest X-ray ^[2]. If the doctor thinks your symptoms could be cancer, you may get an urgent referral to a hospital specialist. The NHS stresses that a referral does not definitely mean you have cancer ^[2].

The main tests at the hospital are ^[4]:

• CT scan. An imaging scan that gives detailed pictures of the chest.
• Bronchoscopy. A thin, flexible tube with a small camera is passed down the throat into the lungs so doctors can look inside.

If cancer is confirmed, more tests may be needed, such as an MRI scan, a PET scan, a biopsy (a small sample of tissue checked under a microscope), blood tests and genetic testing. These show the type of cancer, how far it has spread and whether it has been caused by certain changes in the genes, and the specialist team uses the results to decide what treatment you need ^[4]. The WHO adds that this kind of molecular testing helps guide treatment choices ^[1].

You may get some results on the same day, or after a few days or weeks, and you can call the hospital or your doctor if you are worried, as they may be able to tell you if your results are ready ^[4].

5. Treatment and management

The treatment plan depends on the size of the cancer and where it is, the type of lung cancer, whether it has spread, whether it has certain gene changes, your general health and which options you decide are right for you ^[5]. The main options are ^{[5, 6]}:

• Surgery to remove the cancer, which may mean taking out part or all of a lung.
• Chemotherapy, which uses medicines to destroy cancer cells. It may be used before surgery to shrink a tumour, after surgery to lower the chance of the cancer returning, or when surgery is not possible.
• Radiotherapy, which aims beams of radiation at the tumour. It may be used when surgery is not an option, after surgery, or when the cancer has spread.
• Targeted medicines and immunotherapy. Targeted medicines kill cancer cells or stop them growing as quickly, while immunotherapy uses medicines to help your immune system kill cancer. The NHS says they are sometimes used for advanced lung cancer that has spread to other parts of the body ^[5].

Treatments are often combined. The WHO says multidisciplinary care, meaning a team of different specialists, is essential, and that supportive and palliative care, which focus on easing symptoms and improving quality of life, play an important role at all stages of the disease ^[1]. If advanced lung cancer cannot be cured, the NHS explains that the aim of treatment is to slow the growth and spread of the cancer, help with symptoms and help you live longer, and a symptom control or palliative care team can help ^[5]. The WHO says clinical trials can give access to new treatments, and the National Cancer Institute lists trials for lung cancer ^{[1, 6]}. Ask your specialist whether a trial could be an option.

6. Prevention and screening

The WHO states that not smoking tobacco is the most effective way to prevent lung cancer. Avoiding secondhand smoke, air pollution and workplace hazards such as asbestos and other chemicals also lowers risk ^[1]. The National Cancer Institute lists support for quitting smoking among its prevention resources ^[6].

Screening means testing people who have no symptoms. The WHO says that in well-resourced health systems, screening can be considered for people at high risk, particularly current or former heavy smokers, and that it has reduced lung cancer deaths when it comes with quality checks and follow-up care ^[1]. The National Cancer Institute offers a summary of screening tests with their possible benefits and harms, and a guide to low-dose CT scans for lung screening ^[6]. Ask your doctor whether screening is available and suitable for you.

7. When to see a doctor

The NHS advises seeing a doctor if you have had a cough for more than three weeks or have any other symptom of lung cancer ^[2]. Ask for an urgent appointment if you have coughed up blood or seen blood on a tissue after coughing ^[2].

Get emergency help straight away if you are struggling to breathe, for example gasping or unable to speak, or if you have pain in the chest or upper back. Do not drive yourself, and bring the medicines you take ^[2].

In an emergency, call your local emergency number (112 in India, 911 in the United States).

8. Conclusion

Lung cancer is a major cause of illness worldwide, and smoking is the largest risk factor. The most useful steps are to avoid tobacco and smoke, to take a long-lasting cough or other warning sign seriously, and to see a doctor early. If lung cancer is diagnosed, a specialist team plans treatment based on the type, the spread and your overall health, and supportive care is available alongside it. Tell your doctor about every treatment you use.