Small cell lung cancer: Carcinoma

• What is Small Cell Lung Cancer (Carcinoma of the Lung)
• Statistics on Small Cell Lung Cancer (Carcinoma of the Lung)
• Risk Factors for Small Cell Lung Cancer (Carcinoma of the Lung)
• Progression of Small Cell Lung Cancer (Carcinoma of the Lung)
• Symptoms of Small Cell Lung Cancer (Carcinoma of the Lung)
• Clinical Examination of Small Cell Lung Cancer (Carcinoma of the Lung)
• How is Small Cell Lung Cancer (Carcinoma of the Lung) Diagnosed?
• Prognosis of Small Cell Lung Cancer (Carcinoma of the Lung)
• How is Small Cell Lung Cancer (Carcinoma of the Lung) Treated?
• Small Cell Lung Cancer (Carcinoma of the Lung) References

What is Small Cell Lung Cancer (Carcinoma of the Lung)

Small cell lung cancer is a type of lung cancer. Small cell lung cancer is thought to arise from neuroendocrine cells which form part of the epithelium (lining) of the bronchi (airways).

Statistics on Small Cell Lung Cancer (Carcinoma of the Lung)

Lung cancer is common. One in every 28 Australians will develop lung cancer during their lifetime. Lung cancer is also deadly: it is the commonest cause of cancer death in Australia, accounting for around 23% of male and 15% of female cancer deaths. Lung cancer is more than twice as common in men as in women. Geographically, the tumour is found worldwide, but it is especially common in countries with high tobacco consumption. Small cell carcinoma of the lung accounts for about 18% of all cases of lung cancer.

Risk Factors for Small Cell Lung Cancer (Carcinoma of the Lung)

Cigarette smoking is the main predisposing factor. In recent years, it has been recognised that passive smoking (e.g. from a first degree relative in a house of smokers) can also put people at risk. Generally, the risk increases with the number of cigarettes smoked. The link between cigarette smoking and small cell carcinoma is very strong. Exposure to asbestos increases the risk of developing this tumour. The combination of asbestos exposure plus cigarette smoking is particularly harmful. Other occupational exposures such as exposure to metals including arsenic, chromium and nickel can also increase risk. Some studies have suggested that diet can play a role in lung cancer risk. Though it is not known how it works, diets high in fruits and vegetables seem to decrease risk. Radiation exposure damages the DNA material within the cells and can also cause lung cancer. Radon (a radioactive gas) exposure from our normal surrounding environment, if higher than normal, can predispose to lung cancer. This evidence is mainly based upon population studies which show that people living in areas with a high radon content are prone to increased incidences of a variety of cancers.

Progression of Small Cell Lung Cancer (Carcinoma of the Lung)

Small cell lung cancers behave very differently from most other types of lung cancer (known as non-small cell lung cancers). Small cell lung cancers are very aggressive. They grow quickly and spread via the bloodstream to the liver, lung, bones and brain. It is quite common for tumour deposits to be found in these organs at the time of diagnosis.

Symptoms of Small Cell Lung Cancer (Carcinoma of the Lung)

Patients with small cell carcinoma of the lung may notice:

• Coughing(8-75%)
• Weight loss(0-68%)
• Shortness of breath(3-60%)
• Chest pain(20-49%)
• Haemoptysis (coughing up blood): sputum may be streaked with blood
• Non-specific symptoms: fever, weakness, lethargy.

Rarely, patients may present with difficulty swallowing or wheezing. It is not uncommon for patients with small cell carcinoma to present with symptoms of metastasis (spread) to other areas of the body. For example, a patient with metastatic spread to the bone might present with bone pain, or a patient with spread to the brain may present with headache or seizures.

How is Small Cell Lung Cancer (Carcinoma of the Lung) Diagnosed?

• Full blood picture: this may reveal anaemia(low haemoglobin).
• Liver function tests: abnormal liver function tests may suggest that the tumour has spread to the liver.
• Urea and electrolytes: low levels of sodium in the blood may indicate inappropriate secretion of ADH (SIADH), a complication of some types of lung cancer. Imaging tests:
• Chest x-ray: lung cancer may be seen on chest x-ray as a solitary pulmonary nodule or mass. As many as 80% of solitary pulmonary nodules (CT: this is more accurate than chest x-ray, and may be particularly useful in identification of lymph node involvement. See the example image below.
  
• PET scanningcan help to distinguish between benign and malignant solitary pulmonary nodules seen on chest x-ray. PET scanning may also be used in the assessment of nodal spread and metastatic disease.
• Imaging of other organs: if it is suspected that the cancer has spread to other organs, scans of the liver, brain or bone may be required. This is often necessary in small cell lung cancer as metastasis (spread) at diagnosis is so common. While imaging tests are helpful in raising the suspicion of lung cancer, diagnosis requires that cancer cells are seen under a microscope. There are a number of ways of obtaining samples of suspected cancer cells:
• Fine needle aspirationbiopsy through the skin may be used to investigate suspected lung tumours located on the outside of the lungs.
• Sputum cytology: cells from the sputum (spit) are examined for signs of malignancy (cancer).
• Bronchoscopy with washings, brushings and biopsy: a bronchoscopy is a camera tube placed through the throat into the airways of the lungs. Samples of the cells from the airways can be taken with washing, brushing, or biopsy.

Prognosis of Small Cell Lung Cancer (Carcinoma of the Lung)

Estimates of prognosis (probable outcome) of small cell lung cancer are based on cancer staging. Unlike non-small cell lung cancers, small cell lung cancer staging does not use the TNM (tumour, node, metastasis) system. Instead, the staging system for small cell lung cancers divides them into two groups only: ‘limited disease’ or ‘extensive disease’. In limited disease, the tumour involves only one half of the chest and the lymph nodes draining that half of the chest. Extensive disease refers to any cancer more advanced than this. Limited disease has a better prognosis (outcome) than extensive disease. Overall, small cell carcinoma of the lung is associated with the poorest prognosis of all types of lung cancer. Untreated, survival may be as short as 6-17 weeks. With treatment, 5-year survival still only reaches 5%. This is because most cancers have spread widely at diagnosis so that surgery is not possible.

How is Small Cell Lung Cancer (Carcinoma of the Lung) Treated?

Surgical treatment:

• Small cell lung cancers have usually spread by the time they are diagnosed, and are only very rarely able to be surgically removed. Surgery is therefore not used very often in the treatment of small cell lung cancer.

Chemotherapy:

• Chemotherapy can increase patient survival in small cell lung cancer from as little as 17 weeks to 60 weeks.
• If chemotherapy is to be used, combination regimes that contain platinum-based drugs produce the best results.

Radiotherapy:

• Patients who have ‘limited stage’ SCLC often benefit from radiotherapy to the chest wall.
• Radiotherapy may also be used to treat brain metastasis (spread of cancer to the brain) or to prevent this spread if it has not already occurred (known as prophylactic cranial irradiation).
• While responses to radiotherapy are usually good in small cell carcinoma, it is only very rarely curative – that is, it may temporarily shrink the tumour and improve survival, but does not often cure the disease.

Palliative care Lung symptoms commonly reported by patients with incurable lung cancer include shortness of breath from pleural effusion, coughing, or haemoptysis (coughing up blood). Pain may be from the lung tumour itself, or from spread (metastasis) to other organs, including bone. Treatment is available for all of these symptoms. In some cases, radiotherapy may be used to manage cancer pain. Spinal cord compression is a complication of cancer spread to the spine which requires urgent treatment.

Small Cell Lung Cancer (Carcinoma of the Lung) References

1. Alberg AJ, Samet JM. ‘Epidemiology of lung cancer’, Chest. 2003, 123:21S-49S
2. Beckles MA, Spiro SG, Colice GL, Rudd RM. ‘Initial evaluation of the patient with lung cancer: symptoms, signs, laboratory tests and paraneoplastic syndromes,’ Chest. 2003, 123:97S-104S
3. Braunwald, Fauci, Kasper, Hauser, Longo, Jameson. Harrison’s Principles of Internal Medicine. 16th Edition. McGraw-Hill. 2005.
4. Cotran RS, Kumar V, Collins T. Robbins Pathological Basis of Disease Sixth Ed. WB Saunders Company 1999.
5. The Cancer Council Australia. ‘Clinical Practice Guidelines for the Prevention, Diagnosis and Management of Lung Cancer’ [online]. National Health and Medical Research Council. 2004. Available at URL: http://www.nhmrc.gov.au/publications (last accessed 1/4/07)
6. Talley NJ, O’Connor S. Clinical Examination Fourth Ed. MacLennan & Petty 2001.