Lung Cancer

Abstract

Lung cancer is the 3rd most common cancer in the UK, with around 48,000 lung cancer-related 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, haemoptysis, chest pain, weight loss and malaise, although it is often asymptomatic.
Examples of paraneoplastic syndromes include hypercalcaemia, thrombocytosis and SIADH.
Lung malignancies are staged using the TNM staging system.

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.

Statistics

Lung cancer is the 3^rd most common cancer in the UK, with around 48,000 lung cancer-related deaths in the UK every year – the most common cause of death from cancer for both males and females. It has a 10% survival rate, and in 2015 it is thought that 79% of lung cancers in the UK were preventable. (Source)

Risk Factors

The biggest risk factor for developing lung cancer is tobacco smoking.

Other less common risk factors include occupational carcinogens (namely asbestos and radon) and genetics.

Types

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 diagnosis. Generally, non-small cell lung cancers metastasise slower, meaning localised treatment options like surgery are more successful.

Squamous cell carcinoma makes up around 40% of lung cancer and can be associated with paraneoplastic syndrome releasing PTHrP (see later).
Adenocarcinoma makes up around 35% of lung cancer and is the type of lung cancer most commonly associated with non-smokers (source).
Large cell carcinoma makes up the remaining 5% of lung cancers attributed to NSCLC.

Small cell lung cancers make up around 15% of lung cancers, and are more commonly associated with paraneoplastic sydromes. They commonly metastasise rapidly, but are often chemo-responsive.

Mesothelioma is a cancer of the pleura, and one of the main risk factors for this condition is asbestos exposure.

Signs and Symptoms

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 doesn’t go away or get worse
Dyspnoea
Haemoptysis
Chest or shoulder pain
Weight loss
General malaise

Lung cancer spreads to other parts of the body via the lymphatic system, and symptoms of metastatic spread are dependent on the places they have spread to:

Face bloating (due to compression of the superior vena cava)
Voice hoarseness (due to compression of the left recurrent laryngeal nerve)
Dyspnoea – as a result of the primary tumour itself, or due to anaemia (as a paraneoplastic syndrome), or pleural/pericardial effusions caused by regional metastases.
Dysphagia (due to compression of the oesophagus)
Bone pain or fractures (due to distant metastatic spread)
Central nervous system symptoms
Metabolic symptoms, such as thirst, constipation, and seizures (as part of a paraneoplastic syndrome of ADH release)

Clinical signs of lung cancer can include:

Finger clubbing
Cachexia
Pale conjunctiva associated with anaemia
Cervical lymphadenopathy 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. This is often associated with Pancoast tumours, which occur in the very top of the lungs.
Pleural effusion
Muffled heart sounds
Hepatomegaly
Skin lesions consistent with metastases

Paraneoplastic Syndromes

Paraneoplastic syndromes are triggered by an abnormal immune response to cancer, and are common in certain types of lung cancer. If a patient presents with symptoms of any of these conditions, it is important to rule out lung cancer as a cause.

Examples include:

For small cell lung cancer:

Abnormal release of ADH, resulting in SIADH and abnormal water retention.
Abnormal release of ACTH, causing increased release of cortisol that results in Cushing’s Syndrome.
Lambert-Eaton Syndrome – where the body attacks the neuromuscular junctions causing myasthenia.

For squamous cell carcinoma – release of parathyroid hormone related peptide (PTHrP) which stimulates PTH receptors, causing a syndrome of hypercalcaemia called humeral hypercalcaemia of malignancy.

For adenocarcinomas – hypertrophic pulmonary osteoarthropathy (a triad of serositis, finger clubbing and arthropathy of the large joints).

Staging and Management

Lung malignancies are staged via the TNM staging method, which can be determined using a variety of imaging methods, depending on the type, size and associated symptoms of the malignancy. Examples of imaging modalities include chest x-ray, staging chest CT, PET scan and MRI scan.

Tissue sampling can be obtained via methods including CT biopsy, bronchoscopy and ultrasound-guided biopsy.

It is important to determine the stage of cancer as this can be used to guide treatment options, with stage I more likely to respond to radical therapy, but stage IV management is more likely to be centred around palliation.

Prognosis is generally poor in lung malignancies as the cancer has usually already metastasised by the time it becomes symptomatic. Examples of treatment options include surgery (normally for non-small cell carcinoma), radiotherapy (either radical or palliative), chemotherapy (can be radical, neoadjuvant, or adjuvant) or palliative care (if the cancer is too advanced).

Edited by: Dr. Maddie Swannack

Reviewed by: Dr. Thomas Burnell

Quiz