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Cancer of the lung

Lung cancers are cancers of the lining cells of the air tubes (bronchi). The medical term for lung cancer is bronchial carcinoma.

Lung cancer is the most common cancer in men and the third most common cancer in women, after cancer of the breast and colorectal cancer. In 1998 there were around 38,800 new cases of lung cancer diagnosed in the UK, most of which occurred in people over the age of 45. In 2002, there nearly 29,000 deaths from lung cancer in the UK. The disease is the second most common cause of death in women, after breast cancer.

There are different types of lung cancer depending on which type of cell in the lungs becomes cancerous.

Lung cancer is uncommon before the age of 40. Only about 1 case in 100 is diagnosed in people younger than 40. The great majority of cases occur in people over the age of 60. Everyone with suspected lung cancer is entitled to see a specialist within two weeks of the GP deciding that they need to be seen urgently and requesting an appointment.

The lining cells of the air tubes in healthy lungs are tall (columnar), and the surfaces nearest the inside of the tube are covered with fine hairs (cilia) that move together. The movement of the cilia acts to carry dust and smoke particles and other foreign material upwards and away from the deeper parts of the lungs.

In people who smoke cigarettes, these important cells soon suffer three obvious changes:

  • first, the cilia disappear,
  • then the number of cells increases, and
  • finally the cells become flattened, so that the columnar lining is replaced by an abnormal scaly layer.

This may eventually develop into bronchial carcinoma.The more cigarettes are smoked, the more marked the early cell changes become. The loss of cilia and flattening of the columnar cells occurs much more frequently in cigarette smokers than in those who smoke pipes or cigars. People who have given up smoking have fewer affected cells than smokers, and the number of affected cells becomes progressively less as the number of years of non-smoking increases.

Bronchial carcinoma may extend in various ways. The tumour may grow within the air tube (bronchus) until it causes obstruction and collapse of the part of the lung beyond it, or it may penetrate through the wall to invade the surrounding lung tissue and even the chest wall.

When this happens, the involvement of the nerves between the ribs, or of the ribs themselves, causes great pain. The tumour may spread into the partition between the lungs (the mediastinum) to involve the heart, the gullet (oesophagus), the windpipe (trachea), the large veins returning blood to the heart, or the nerves to the voice box (larynx).

Loss of the voice may be the first sign of lung cancer. Spread also occurs to nearby lymph nodes and, by way of the bloodstream, to the bones, brain, skin, liver and other organs.

The outlook for people with lung cancer is not good. Only 20% of people are alive one year after being diagnosed with the disease, and only 8% survive for five years.