Lung Cancer

What is lung cancer?

Lung cancer develops in the lungs — the two spongy organs inside the chest that allow us to breathe. There are several types, but the most common are:

• Non-small cell lung cancer (NSCLC): accounts for approximately 80–85% of all lung cancers. Its three best-known subtypes are squamous cell carcinoma, adenocarcinoma and large cell carcinoma.
• Small cell lung cancer (SCLC): accounts for about 10–15% of all lung cancers and tends to spread very quickly. Around 70% of people with SCLC are diagnosed at stage 4, once the cancer has already spread.

Lung cancer is the second most common cancer in the world and the leading cause of cancer death worldwide, among both men and women. In the United States, the American Cancer Society estimated for 2020 about 228,820 new cases (116,300 in men and 112,520 in women) and about 135,720 deaths (72,500 in men and 63,220 in women). Even so, with today's screening programmes and treatments, lung cancer is often manageable when it is identified early.

What causes lung cancer?

Although tobacco smoking is best known as a risk factor, research has shown that it can lead to lung cancer even though it is not the only cause; it accounts for around 80% of all lung cancers.

At a cellular level, gene mutations can alter the DNA of a lung cell and transform it into a cancerous one. Cancer begins in a single cell and then grows and spreads from there. Two kinds of genes are particularly involved in this process — oncogenes and tumour suppressor genes. Some of the changes that lead to these mutations are inherited, while others are acquired during life.

Risk factors

• Smoking: tobacco smoking is the single strongest risk factor for lung cancer.
• Second-hand smoke: breathing in the smoke of others is far from harmless and is almost as dangerous as smoking yourself.
• Exposure to cancer-causing substances: contact with agents such as radon, asbestos and arsenic significantly raises the risk.
• Previous radiotherapy: radiotherapy to the chest for another cancer increases the risk of later developing lung cancer.
• Family history: having a first-degree relative with lung cancer raises your own risk, particularly if they were diagnosed at a younger age.
• Personal history: a previous lung cancer diagnosis increases the chance of developing it again.

Signs and symptoms

Lung cancer is often symptomless in its early stages, with symptoms tending to appear only once it is more advanced. Signs to be aware of include:

• a persistent cough that gradually worsens
• coughing up blood
• chest pain
• hoarseness of the voice
• unexplained weight loss
• loss of appetite
• fatigue and weakness
• shortness of breath (dyspnoea)
• wheezing (a whistling sound when breathing)
• repeated or persistent chest infections
• bone pain, changes in the nervous system, or jaundice, if the cancer has spread
• swollen lymph nodes, if the cancer has spread

How it's diagnosed

Lung cancer may be diagnosed using one or more of the following:

• Imaging tests: a CT scan or X-ray can reveal a lesion or mass in the lungs.
• Sputum cytology: if a persistent cough produces sputum, examining it under a microscope can reveal cancer cells.
• Needle biopsy: taking a tissue sample from the mass to determine its nature and, if cancer is confirmed, its type.
• Bronchoscopy: passing a lighted tube down the throat and into the lungs to look for abnormal cells.
• Mediastinoscopy: inserting instruments through a small incision at the base of the neck to take samples from the lymph nodes when cancer is suspected.

Treatment options

Once lung cancer has been diagnosed, your doctor will establish its stage and then discuss the options best suited to your overall health, medical history and staging results. Treatment may include:

• Surgery: the type depends on the size and location of the cancer:
• pneumonectomy — removing an entire lung
• lobectomy — removing a whole lobe of a lung
• segmental resection — removing a larger portion of a lung, but not a whole lobe
• wedge resection — removing a small section of lung containing the tumour, along with a margin of healthy tissue
• Chemotherapy: drugs given intravenously or orally to kill cancer cells, either as a single drug or a combination, over a period of weeks or months.
• Radiotherapy: high-powered energy beams, from sources such as X-rays and protons, used alone or alongside chemotherapy.
• Targeted drug therapy: drugs that act on specific abnormalities within cancer cells.
• Immunotherapy: immune cells, or drugs that prompt the immune system, used to kill cancer cells.
• Alternative treatments: other evidence-based approaches used to attack cancer cells.

Reducing your risk

There is no guaranteed way to prevent lung cancer, but reducing your exposure to its risk factors can lower your chances of developing it:

• avoid smoking, or stop if you currently smoke
• avoid second-hand smoke
• limit exposure to cancer-causing gases
• test your home for radon
• eat a healthy diet
• exercise on most days of the week