Lung cancer

What is it?

According to WHO, lung cancer occurs "when abnormal cells grow uncontrollably in the lungs". MedlinePlus defines it as cancer that forms in lung tissue, usually in the cells lining the air passages. WHO describes it as the leading cause of cancer cases and deaths worldwide, with about 2.5 million new cases and 1.8 million deaths in 2022.

It has two main types (NCI, WHO): non-small cell lung cancer (NSCLC), which accounts for about 85% of cases according to WHO, and small cell lung cancer (SCLC), which accounts for about 15% according to MedlinePlus and is fast-growing and tends to spread faster. MedlinePlus says the two types grow and are treated differently. The NCI lists three main types of non-small cell: squamous cell carcinoma (in the thin, flat cells lining the lung), adenocarcinoma (in the mucus-secreting cells), and large cell carcinoma.

The NHS says the seriousness of lung cancer depends on its size, whether it has spread, and the patient's general health. This page does not cover the rare childhood lung tumours the NCI refers to.

Causes

Smoking is the main cause: according to the CDC, "cigarette smoking is the number one risk factor for lung cancer", and it is linked to about 80% of lung cancer deaths in the United States; smokers are 15 to 30 times more likely to develop or die from it than non-smokers, and even smoking a few cigarettes a day or smoking occasionally raises the risk. MedlinePlus states that smoking causes about 9 in 10 cases in men and about 8 in 10 in women. WHO states that tobacco smoking (cigarettes, cigars and pipes) is the main risk factor, and that most preventable cases are attributed to it (60–70%), followed by air pollution and occupational exposure.

Non-smokers can also be affected (NCI). The NHS says the cause is not always known and may be linked to lifestyle, genetic changes and environmental factors. For small cell cancer specifically, MedlinePlus says almost all cases are caused by cigarette smoking and that it is very rare in people who have never smoked.

Radon: a gas that forms naturally in rocks, soil and water and can accumulate inside buildings; the CDC considers it another important cause of lung cancer, and the risk grows over time, especially in smokers. The NHS lists long-term radon inhalation among the risk factors.

Risk factors

Other risk factors according to WHO, the CDC, MedlinePlus and the NHS: passive smoking; outdoor and household air pollution; occupational exposure to asbestos, silica, diesel exhaust, arsenic, chromium, beryllium, nickel, soot and tar; personal or family history of lung cancer; HIV infection; previous chest radiotherapy; chronic lung disease and genetic predisposition (WHO).

The NHS states that having chronic obstructive pulmonary disease raises the risk of lung cancer. The CDC states that beta-carotene supplements raise the risk, especially in heavy smokers who drink alcohol daily, and that well water contaminated with arsenic or radon also raises the risk.

Age: MedlinePlus says non-small cell lung cancer is more common in older people and rare before age 45, and that the risk rises with the number of cigarettes smoked per day and the length of time smoked.

Symptoms

The CDC says most people with lung cancer have no symptoms until the cancer has advanced, and WHO says early symptoms may be mild or mistaken for ordinary breathing problems.

Common symptoms (WHO, CDC, NHS, MedlinePlus): a cough that does not go away or gets worse, shortness of breath, chest or shoulder pain, coughing up blood, wheezing, persistent tiredness, unexplained weight or appetite loss, and repeated chest infections or repeated bouts of pneumonia.

Less common symptoms (NHS, MedlinePlus): swelling of the face or neck or bulging neck veins, difficulty swallowing, hoarseness that does not go away, and changes in the shape of the fingertips (they look wider or curve downwards). In late stages there may be bone pain or tenderness, a drooping eyelid, joint pain, nail problems and weakness (MedlinePlus). If the cancer has spread to other parts of the body, symptoms may be specific to that part (CDC).

The CDC and NHS stress that these symptoms can be caused by many other conditions; what is needed is to see a doctor to find the cause. The NHS advises seeing a doctor if a cough lasts more than 3 weeks, and says that detecting cancer early may make it easier to treat.

How is it diagnosed?

According to MedlinePlus, the healthcare provider takes a medical and family history and does a physical examination, then requests imaging such as a chest X-ray or a chest CT scan, blood and sputum tests, and may take a lung biopsy. WHO lists imaging (X-ray, CT and MRI), bronchoscopy, sampling and molecular tests.

The NHS states that the two main tests when cancer is suspected are a CT scan and a bronchoscopy, in which a thin, flexible tube with a small camera is passed through the throat into the lungs. Sampling methods according to MedlinePlus and the NCI include: bronchoscopy with biopsy, CT-guided needle biopsy, endobronchial ultrasound (EBUS), mediastinoscopy, thoracoscopy, open lung biopsy, and pleural biopsy or drainage of pleural fluid.

After confirmation, further tests may be done, including MRI (including a brain MRI), positron emission tomography–CT (PET-CT), a bone scan, lung function tests, blood tests and genetic tests on the sample; the results show the type of cancer, how far it has spread and whether it was caused by changes in certain genes (NHS, NCI). The NHS says some results may arrive the same day and others after days or weeks.

Stages according to MedlinePlus: non-small cell has 5 stages, from stage 0 (has not spread beyond the inner lining of the lung) to stage 1 (small and has not reached the lymph nodes), stage 2 (reached some nearby nodes), stage 3 (spread to nearby tissues or distant nodes) and stage 4 (spread to other organs such as the other lung, brain, liver or bones). Small cell is classified as "limited" within the chest or "extensive" beyond it.

Screening: according to the CDC, the US Preventive Services Task Force (USPSTF) recommends annual low-dose CT (LDCT) screening for those who meet all three conditions: age 50 to 80, a smoking history of 20 pack-years or more, and currently smoking or having quit within the past 15 years; screening stops at age 81, 15 years after quitting, or when a health problem prevents surgery. Its harms according to the CDC include false-positive results, overdiagnosis of cancers that might never have caused a problem, and radiation from repeated screening. WHO says screening can be considered in well-resourced health systems for specific high-risk groups, especially current and former heavy smokers. These recommendations differ between countries, and the doctor decides what suits each person.

Treatment

The treatment categories usually used are listed here; this is not a prescription. The doctor chooses the plan according to each person's condition; do not change any medicine or dose without a specialist.

The plan is chosen with a specialist team according to the size, location and type of the cancer and whether it has spread, genetic changes, general health and the patient's preferences, and more than one method may be combined (NHS). The NCI states that prognosis and treatment options depend on the stage, the type, the presence of mutations in certain genes, the presence of symptoms and general health. The team explains the treatments, their benefits and their side effects, and draws up the plan with the patient (NHS).

Surgery: to remove the cancer; part of the lung or the whole lung may be removed (NHS). Types include wedge resection, segmentectomy, lobectomy, pneumonectomy and sleeve resection (WHO, NCI). In early stages of non-small cell cancer, surgery may offer a cure (MedlinePlus).

Radiotherapy directs beams of radiation straight at the tumour (NHS), and is used when surgery is not possible, to relieve symptoms, or to treat small tumours (MedlinePlus). Chemotherapy is a medicine that kills cancer cells, and may be given when surgery is not possible or the cancer has spread, before surgery to shrink the tumour, or after it to reduce the risk of recurrence (NHS).

Targeted therapy aims at specific molecules in or on cancer cells to kill them or slow their growth, and immunotherapy helps the immune system kill the cancer; it is given alone or with chemotherapy, and MedlinePlus says it is now often used before surgery (NHS, MedlinePlus). Other treatments mentioned include laser, photodynamic therapy, cryotherapy, electrocautery and placing a stent by endoscopy (MedlinePlus, NCI).

In small cell cancer, intravenous chemotherapy is the mainstay, and radiotherapy and immunotherapy may be added, while surgery helps only a very small number because the disease has usually already spread (MedlinePlus).

WHO says supportive and palliative care is essential at all stages to relieve symptoms and pain and improve quality of life for the patient and family, and in advanced disease the patient is referred to a symptom control or palliative care team (NHS). Clinical trials are available for all stages (NCI). A patient should not start or stop any treatment without the treating team.

Follow-up

The NCI says some tests are repeated from time to time after treatment ends to see how well it worked and to detect any return of the cancer. A team of specialists accompanies the patient, usually including a clinical nurse specialist who is the main point of contact during and after treatment (NHS). This page does not cover detailed follow-up schedules.

Complications

The cancer may spread to the bones, liver, lymph nodes, other parts of the lung and the brain (MedlinePlus). The CDC mentions repeated bouts of pneumonia and enlarged lymph nodes inside the chest. WHO says it is often diagnosed at advanced stages when treatment options are limited.

Prognosis according to MedlinePlus: in non-small cell cancer, survival and cure rates are higher in stages 1 and 2, stage 3 may be cured in some cases, while stage 4 is rarely cured and the aim of treatment is to prolong life and improve its quality. Small cell cancer is very serious, few patients are alive after 5 years, although treatment often prolongs life to more than 12 months. These are general figures, and the doctor discusses each patient's situation.

Prevention

"Not smoking tobacco is the best way to prevent lung cancer" (WHO). MedlinePlus advises quitting smoking and not starting in the first place, reducing exposure to workplace hazards, testing the home for radon and reducing it, and avoiding passive smoking. The CDC says the risk falls after quitting smoking.

The NHS adds regular physical activity and a healthy diet that includes at least 5 portions of fruit and vegetables a day. At the community level, WHO calls for smoke-free environments, tobacco control policies, addressing occupational hazards and reducing air pollution.

Living with it

MedlinePlus says joining a support group may ease the stress of the illness and reduce feelings of isolation. The treating team helps manage the side effects of treatment, and in advanced disease the palliative care team controls symptoms and links the patient to other kinds of support (NHS). This page does not cover living with lung cancer in detail.

Common questions