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Lung Cancer

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Overview

Around 95% of primary lung tumours are bronchial carcinomas. Primary bronchial cancers can be subdivided into 2 types based on their management and prognosis:

  • Non-small cell lung cancers (NSCLCs) – around 85% of cases
  • Small cell lung cancers (SCLCs) – around 15% of cases

Lung cancer metastases are common and typical sites are the bone, kidney, breast, prostate, GI tract, ovaries, and cervix. 

Types

Non-small cell lung cancers (NSCLCs)

They can be further divided into:

  • Adenocarcinoma:
    • Most common type
    • Often seen in non-smokers
  • Squamous carcinoma:
    • Often presents as an obstruction of the bronchus leading to infection
  • Large cell carcinoma
  • Carcinoid tumours

Small cell lung cancers (SCLCs)

Small cell lung cancers (SCLCs) arise from Kulchitsky cells which are part of the amine precursor uptake and decarboxylation (APUD) system. APUD cells make polypeptides and amines that act as hormones or neurotransmitters. SCLCs often have paraneoplastic features (see below) as a result of this.

SCLCs carry a poor prognosis as they are aggressive and rapidly growing. They often spread early and are nearly always inoperable at presentation.

Epidemiology

  • Lung cancer is the second most common cancer in the UK following breast
  • Around 90% of lung cancers are caused by smoking
  • Adenocarcinoma is the most common type of lung cancer

Risk Factors

Presentation

General features

The key general symptoms in patients with lung cancer are:

  • Dyspnoea
  • Cough:
    • A new or persistent cough in a former smoker should raise suspicion of cancer
  • Haemoptysis:
    • A red-flag symptom of cancer
  • Unexplained weight loss:
    • A red-flag symptom of cancer
  • Chest pain or discomfort:
    • Due to tumours invading the pleura/chest well (the lung tissue itself does not have pain fibres)
  • Hoarseness:
    • Some tumours, particularly Pancoast tumours (tumours of the apex of the lung) can press on the recurrent laryngeal nerve, leading to hoarseness
  • Horner’s syndrome
  • Features of paraneoplastic syndromes – see below

Features of complications

  • Superior vena cava obstruction (SVCO) can occur if a tumour compresses the superior vena cava resulting in:
    • Facial swelling
    • Distended neck veins
    • Raised jugular venous pressure
    • Blurred vision
  • Features of brain metastases may be:
  • Bone metastases can lead to bone pain and/or fractures

Examination findings

Some signs on examination may be:

  • Cervical or supraclavicular lymphadenopathy
  • Focal monophonic wheeze
  • Finger clubbing

Paraneoplastic syndromes

Overview

A paraneoplastic syndrome is a set of signs and symptoms emerging as a consequence of a tumour in the body, typically due to the production of molecules (such as hormones) by tumour cells, or the immune response against the tumour itself. Paraneoplastic syndromes vary depending on the type of lung cancer present.

Adenocarcinoma features

  • Gynaecomastia due to ectopic hCG secretion:
    • The hCG acts as LH and stimulates the production of more oestrogen
  • Hypertrophic pulmonary osteoarthropathy (HPOA):
    • Bone pain in the wrists, ankles, and knees with new bone forming around the periosteum
    • This is thought to be due to reduced platelet clearance (which normally occurs in the lungs) leading to increased production of factors contributing to bone growth

Small cell carcinoma

Squamous cell carcinoma 

  • Parathyroid hormone-related protein (PTH-rp) secretion leading to hypercalcaemia
  • Hypertrophic pulmonary osteoarthropathy (HPOA)
  • Ectopic thyroid-stimulating hormone secretion (TSH) leading to thyrotoxicosis

Differential Diagnoses

Small cell lung cancer

  • Although SCLC and NSCLC have similar general features, SCLC typically has the aforementioned paraneoplastic features such as ectopic ADH secretion, ectopic ACTH secretion, and LEMS
  • Finger clubbing and HPOA are less common in small-cell lung cancer
  • Patients who smoke are more likely to be affected

Non-small cell lung cancer

  • Although SCLC and NSCLC have similar general features, NSCLC typically has fewer paraneoplastic features, which may be any of the aforementioned ones
  • Finger clubbing and HPOA are more common in non-small cell lung cancer

Carcinoid syndrome

  • Flushing is a prominent associated feature
  • There is associated diarrhoea

Tuberculosis

  • Signs and symptoms may be difficult to distinguish
  • Chest x-ray shows upper lobe cavitation
  • Sputum culture shows Mycoplasma tuberculosis

Idiopathic pulmonary fibrosis

  • There is also shortness of breath, finger clubbing, and weight loss, however, the cough present is dry and haemoptysis is usually not present

Referral

Refer using a suspected cancer (2-week wait) pathway for lung cancer if:

  • There are chest x-ray features that suggest lung cancer
  • ≥40 years with unexplained haemoptysis

Offer an urgent chest x-ray within 2 weeks if patients have 2 or more of the following, or if they have ever smoked and have one of the following:

  • Cough
  • Fatigue
  • Shortness of breath
  • Chest pain
  • Weight loss
  • Appetite loss

Consider an urgent chest x-ray within 2 weeks if patients are ≥40 with any of the following:

  • Persistent or recurrent chest infections
  • Finger clubbing
  • Supraclavicular or persistent cervical lymphadenopathy
  • Chest signs suggestive of cancer
  • Thrombocytosis – this can be a marker for potential cancers

Investigations

All patients

  • Chest x-rays:
    • The first investigation performed on all patients with suspected lung cancer
  • CT chest with contrast:
    • The investigation of choice for lung cancer
    • The contrast helps differentiate lymph nodes from blood vessels
  • Bronchoscopy:
    • To allow a biopsy to be taken for histological diagnosis
  • Positron emission tomography (PET)-CT scan:
    • Done in potentially curable patients to localise pathology

Other investigations

  • Full blood count (FBC):
    • May show thrombocytosis
  • Liver function tests (LFTs):
    • LFTs may be deranged if liver metastases are present
    • ALP may be raised suggesting bone metastases
  • Urea and electrolytes (U&Es):
    • May show hyponatraemia due to SIADH
  • Bone scan:
    • For skeletal metastases
  • CT or MRI of the brain:
    • For brain metastases which appear as enhancing masses with surrounding oedema

Diagnosis

Diagnosis is made based on clinical features and investigations. Lung cancer can be staged using the TNM classification system.

Management

Overview

Management options are put in place using a multidisciplinary approach. In NSCLC, surgery may be an option, along with radiotherapy and chemotherapy. Many patients with SCLC, however, have metastases at the time of presentation, and are less suitable for surgery, leaving chemotherapy and radiotherapy as treatment options.

Treatments such as endobronchial stenting and debulking can be used in palliative care to relieve bronchial obstruction.

Complications

Prognosis

  • The ten-year survival rate for lung cancer is <10%
  • SCLC has a poorer prognosis than NSCLC, many patients have extensive disease at presentation

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