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Next Lesson - Respiratory Failure
Contents
Abstract
- Lung cancer is the 3rd most common cancer in the UK and the most common cause of cancer death, with around 32,800 deaths in the UK every year.
- The biggest risk factor for developing lung cancer is smoking.
- Symptoms of lung cancer include a persistent cough, dyspnoea (breathlessness), haemoptysis (coughing up blood), chest pain, weight loss and malaise (feeling generally unwell). Early lung cancer often causes no symptoms (it is asymptomatic).
- Paraneoplastic syndromes are effects of a cancer that are caused by substances the tumour releases, or by the immune response to it, rather than by the tumour spreading. Examples include hypercalcaemia (high blood calcium), thrombocytosis (a raised platelet count) and SIADH (syndrome of inappropriate antidiuretic hormone secretion, which lowers the blood sodium level).
- Lung cancers are staged using the TNM system (tumour, nodes, metastases), which describes the size of the tumour, spread to lymph nodes and spread to other parts of the body.
Core
Please note that this article is just an overview of lung cancer, and will mainly be focused on how lung cancer presents, and not on the specific treatment.
Lung cancer is the 3rd most common cancer in the UK. It is the most common cause of cancer death in the UK, with around 32,800 deaths each year (2022 to 2024). In England, about 18% of people diagnosed with lung cancer survive their disease for 5 years or more (2015 to 2019). In 2015 it was estimated that approximately 79% of lung cancers in the UK were preventable. (Source)
The biggest risk factor for developing lung cancer is tobacco smoking.
Other risk factors include:
- Occupational carcinogens (substances at work that can cause cancer), such as asbestos (a material that was used in some buildings).
- Radon, a naturally occurring radioactive gas that can build up inside buildings in some areas of the UK.
- Air pollution.
- Passive smoking (breathing in other people’s tobacco smoke).
- A family history of lung cancer.
The main categories of lung cancer are non-small cell lung cancer, small cell lung cancer and rare tumours.
Non-small cell lung cancers (NSCLC) make up around 80% of lung cancer diagnoses. They generally spread (metastasise) more slowly than small cell lung cancers. This means that treatment aimed at the tumour itself, such as surgery, is more often successful.
- Squamous cell carcinoma develops in the flat cells that cover the surface of the airways. It accounts for around 25 to 30% of lung cancers. It can be associated with paraneoplastic syndromes, which are effects of a cancer that are not caused by its spread. An example is release of parathyroid hormone related peptide (PTHrP). See Paraneoplastic Syndromes below.
- Adenocarcinoma starts in the mucus-making gland cells in the lining of the airways. It is the most common subtype, accounting for around 40% of lung cancers. It is also the most common subtype in people who have never smoked, although it occurs in people who smoke too (source).
- Large cell carcinoma is a less common type of NSCLC. Its cancer cells look larger than typical cells under the microscope. There are also other, rarer types of NSCLC.
Small cell lung cancers make up around 15% of lung cancers. They are more commonly associated with paraneoplastic syndromes. Small cell lung cancers tend to spread (metastasise) early, but are often chemo-responsive (they often respond to chemotherapy, which is treatment with anti-cancer drugs).
Mesothelioma is a cancer of the pleura (the membranes around the lungs). It is usually caused by asbestos exposure.
The symptoms of lung cancer depend on how far it has spread. The presence of a primary lung tumour can be asymptomatic, but symptoms of the tumour can include:
- A persistent cough that does not go away, a new cough, or a change in an existing cough (for example, it gets worse)
- Dyspnoea (breathlessness)
- Haemoptysis (coughing up blood)
- Chest or shoulder pain
- Weight loss
- General malaise (feeling generally unwell)
Lung cancer can grow into nearby structures, such as nerves, the oesophagus and large blood vessels in the chest. It can also spread to lymph nodes and to other parts of the body. The symptoms of metastatic spread depend on where the cancer has spread to. Some of the symptoms below are caused by the tumour pressing on nearby structures, or by paraneoplastic syndromes (see Paraneoplastic Syndromes below):
- Swelling of the face and neck (due to compression of the superior vena cava, the large vein that carries blood from the upper body to the heart)
- Hoarse voice (due to compression of the left recurrent laryngeal nerve, a branch of the vagus nerve that supplies the muscles of the voice box, or larynx)
- Dyspnoea (breathlessness) can have several causes. These include the primary tumour itself and anaemia (common in lung cancer, and linked to inflammation and poor nutrition). Pleural or pericardial effusions (fluid around the lungs or the heart) can also cause it, when the cancer has spread to nearby structures.
- Dysphagia (difficulty swallowing, due to compression of the oesophagus)
- Bone pain or fractures (due to distant metastatic spread)
- Central nervous system symptoms, such as headache, seizures, drowsiness, weakness on one side of the body or changes in behaviour (for example, due to spread to the brain)
- Metabolic symptoms from paraneoplastic syndromes. Release of antidiuretic hormone (ADH) can cause a low blood sodium level, which can cause headache, drowsiness and seizures. Hypercalcaemia (high blood calcium) can cause thirst and constipation.
Clinical signs of lung cancer can include the following. On examination they can show local spread of the tumour, spread to other parts of the body, or a paraneoplastic syndrome:
- Finger clubbing (rounded, bulging fingertips with curved nails)
- Cachexia (severe weight and muscle loss)
- Pale conjunctiva (the thin lining of the inner eyelid and the eye) associated with anaemia
- Cervical lymphadenopathy (swollen lymph nodes in the neck) associated with local lymphatic spread
- Horner’s syndrome: a triad of miosis (constricted pupil), anhidrosis (lack of sweating) and ptosis (eyelid droop) on one side, due to compression of the sympathetic nerve pathways in the neck. Horner’s syndrome is often associated with Pancoast tumours, which occur in the very top of the lungs (the apex). Pancoast tumours can also press on the brachial plexus (the network of nerves that supplies the arm), causing shoulder and arm pain.
- Pleural effusion (fluid collecting between the layers of the pleura around the lung)
- Muffled heart sounds (quiet and hard to hear, for example because of fluid around the heart)
- Hepatomegaly (an enlarged liver)
- Skin lesions consistent with metastases
Paraneoplastic syndromes are clinical features caused by substances produced by tumours, such as ectopic hormone secretion (a hormone made by tissue that does not normally make it) or immune mediated mechanisms, and are common in certain types of lung cancer. If a patient presents with symptoms of a paraneoplastic syndrome, it is important to rule out lung cancer as a cause.
Examples include thrombocytosis (a raised platelet count), which can occur in lung cancer. NICE advises considering an urgent chest X-ray in people aged 40 and over who have thrombocytosis. Other examples include:
For small cell lung cancer:
- Abnormal release of antidiuretic hormone (ADH), resulting in SIADH (syndrome of inappropriate antidiuretic hormone secretion) and abnormal water retention. This lowers the blood sodium level (hyponatraemia).
- Abnormal release of ACTH (adrenocorticotrophic hormone), causing increased release of cortisol that results in Cushing’s syndrome (the effects of too much cortisol).
- Lambert-Eaton syndrome: an autoimmune condition affecting the neuromuscular junction (the point where a nerve signals to a muscle), causing proximal muscle weakness (weakness of the muscles closest to the trunk).
For squamous cell carcinoma: release of parathyroid hormone related peptide (PTHrP), which stimulates parathyroid hormone (PTH) receptors. This causes hypercalcaemia (high blood calcium), called humoral hypercalcaemia of malignancy (humoral means that the cause is a hormone-like substance carried in the blood).
For adenocarcinomas: hypertrophic pulmonary osteoarthropathy. This is a triad of finger clubbing, periostosis (new bone growth along the surface of the long bones) and arthropathy (joint disease, affecting the large joints).
Lung cancers are staged using the TNM staging system. T describes the size and local spread of the tumour, N describes spread to lymph nodes and M describes spread to other parts of the body (metastasis). The stage can be worked out using several imaging tests, chosen according to the type, size and associated symptoms of the cancer. NICE advises a contrast-enhanced CT scan for everyone with known or suspected lung cancer. Contrast is a dye injected into a vein to make structures show up more clearly. The scan covers the chest, including the liver, adrenal glands and lower neck. PET-CT (positron emission tomography combined with CT, which shows where cells are most active) is offered to people who could have treatment with curative intent. MRI is not used routinely to assess the T stage of the primary tumour in non-small cell lung cancer. It is used when necessary for tumours at the top of the lung (superior sulcus or Pancoast tumours).
Tissue sampling (biopsy) is needed to confirm the diagnosis and to identify the type of lung cancer, because this guides treatment. It can be done in several ways. Examples include image-guided biopsy, bronchoscopy and endobronchial ultrasound (EBUS). In image-guided biopsy, a needle is guided into the tumour using imaging such as CT. Bronchoscopy means looking into the airways with a camera on a flexible tube. In EBUS, an ultrasound probe on a bronchoscope guides a needle into lymph nodes or lesions next to the airways. The choice depends on where the tumour is and whether the result will change treatment.
It is important to determine the stage of the cancer because it helps to guide treatment options and gives information about the prognosis. Early stage disease, such as stage I, is more likely to be suitable for radical therapy, which aims to cure the cancer. Some stage III disease can also be treated with curative intent. Stage IV management is more likely to be centred around palliation, which aims to slow the cancer, relieve symptoms and help people live longer rather than to cure it.
Prognosis is generally poor in lung cancer because many people are diagnosed late. In England in 2022, about a third (34%) of lung cancers with a known stage were diagnosed at an early stage (stage I or II). Many are diagnosed when the cancer has already metastasised (spread to other parts of the body) and has become symptomatic (started to cause symptoms).
Examples of treatment options include surgery (normally for non-small cell lung cancer) and radiotherapy (treatment with targeted radiation), which can be radical (aiming to cure) or palliative. Chemotherapy (treatment with anti-cancer drugs) can be radical, neoadjuvant (given before surgery), adjuvant (given after surgery) or palliative. Immunotherapy (medicines that help the immune system attack the cancer) and targeted therapy (medicines that act on specific changes in the cancer cells) are also used for some people with lung cancer. These include people with advanced disease that has spread to other parts of the body. Palliative care (care that relieves symptoms and supports the person and their family) is offered when the cancer is too advanced to cure, and it can also start early, soon after diagnosis.
Edited by: Dr. Maddie Swannack
Reviewed by: Dr. Thomas Burnell and Dr. Marcus Judge
Quiz
- 6024
