BIOLOGY Volume 1 - A Guide to General Biology - 2004

9. UTILIZATION OF ENERGY

9.7. Diseases of the Respiratory System

9.7.5. Lung Cancer

In the UK, Lung Cancer is the most common form of cancer in men (followed by breast cancer in women). It ranks third among the leading causes of mortality in the UK, following cardiovascular disease and stroke (Fig. 9.34). In the 1980s, the mortality rate from lung cancer here was approximately 1 in 18 (5–6%). Cancer is caused by the uncontrolled division of Cells that cease to respond to normal incoming signals. This results in an undifferentiated mass of cells (a tumour; Fig. 9.35). Sometimes cells break away from this mass and are transported (via Blood or Lymph) to other PARTS OF THE body, where they give rise to secondary tumours. Lung cancer typically originates in the bronchiolar epithelium as a so-called bronchial carcinoma and subsequently spreads throughout the Lungs. It is almost invariably caused by cigarette smoking (99.7% of those who die from lung cancer are smokers). This is driven by tars present in cigarette smoke, which contain cancer-causing components ("carcinogens"). Irritation causes the respiratory mucosal epithelium to thicken due to accelerated Cell Division; this may well be what triggers the carcinogenic process. Anti-smoking campaigns have recently been bearing fruit, with lung cancer mortality rates gradually declining (Fig. 9.34).

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Fig. 9.34. Mortality from lung cancer.