Lung Cancer

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Introduction

Lung Cancer, growth of malignant cells affecting, initially, the lung. Cancer forms when a lung cell undergoes alterations to its DNA (see Nucleic Acids), leading to uncontrolled cell growth. Proliferation continues until a tumour forms.

The process of metastasis (spread) takes place when cells break off from the tumour and travel via the blood or lymphatic system, lodging in other organs. There they begin to multiply, forming other tumours.

Lung cancer falls into two groups: small cell and non-small cell carcinomas. Small cell lung cancer (SCLC) is also called oat cell carcinoma because of the cells’ shape. About 25 per cent of lung cancers are of this type.

Non-small cell lung cancer (non-SCLC) comprises squamous cell (or epidermoid) cancer, which arises from cells that line the airways of the lung, and is the most common form of lung cancer; Adenocarcinoma, which arises in mucus-producing cells which line the upper airways of the lung; and large cell carcinoma.

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Symptoms

The symptoms of lung cancer are a persistent hacking cough, blood in the sputum, wheezy breathing, pain in the shoulder or chest, neck or facial swelling, and recurring pneumonia or bronchitis.

III

Statistics

Lung cancer is the biggest cause of cancer death worldwide. In the United Kingdom there were about 33,600 deaths in 2002. It is the most common cancer in men, with about 23,250 cases in 2000 and 20,220 deaths in 2002. In women it is the third most common cancer, with about 15,160 cases in 2000, and ranks first in cancer deaths, with about 13,380 reported in 2002. Incidence and deaths are decreasing in men, but increasing in women (it overtook breast cancer as the primary cause of cancer death in women at the beginning of the 21st century). Lung cancer is most common in individuals over 50 years of age. The highest incidence is in the 65 to 79 age-group.

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Causes

A huge proportion—90 per cent—of lung cancers is caused by smoking. About 6 per cent may be linked to a naturally occurring radioactive gas, radon. Other causes are passive smoking (breathing in smoke from other people’s cigarettes, cigars, or pipes) and exposure to certain substances such as asbestos. Diet may also be involved; studies have shown that a diet low in fresh fruit and vegetables may increase risk.