Cancer is a disease that results from abnormal growth and division of cells that make up the body’s tissues and organs.
Under normal circumstances, cells reproduce in an orderly fashion to replace old cells, maintain tissue health and repair injuries. However, when growth control is lost and cells divide too much and too fast, a cellular mass -or "tumour" -is formed.
If the tumour is confined to a few cell layers and it does not invade surrounding tissues or organs, it is considered benign. By contrast, if the tumour spreads to surrounding tissues or organs, it is considered malignant, or cancerous. In order to grow further, a cancer develops its own blood vessels and this process is called angiogenesis. When it first develops, a malignant tumour may be confined to its original site.
If cancerous cells are not treated they may break away from the original tumour, travel, and grow within other body parts, the process is known as metastasis.
Lung cancer is a growth of abnormal cells inside the lung. These cells reproduce at a much faster rate than normal cells. The abnormal cells stick together and form a cluster or growth, known as a tumour. If the abnormal cells began growing in the lung, this is known as a primary lung tumour.
Types of lung cancer
Depending on how the cells look under a microscope, cancers that begin in the lung are divided into 2 major types:
Non-small cell lung cancer generally spreads to other organs in the body at a slower rate than small cell lung cancer. Non-small cell lung cancer is the most common type of lung cancer, accounting for almost 80 per cent of lung cancers. Small cell lung cancer accounts for about 20 per cent of all lung cancers.
Lung cancer is very difficult to detect at an early stage. Common symptoms include:
There are various treatment options available for lung cancer (with different aims), which include: surgery; chemotherapy; radiotherapy; and laser treatment.
Those non-small cell lung cancers which are amenable to surgery are those where the cancer is confined to a lump in the lung or to the draining lymph nodes immediately next to the lump, but disease where the lymph nodes in the centre of the chest are involved is usually considered not suitable for surgery alone. Investigations include chest x-rays and CT scans. Surgery may involve removal of all the lung or part of the lung. For those cancers that spread to the centre of the chest, a combined treatment approach may involve chemotherapy with radiotherapy and surgery. Patients who present with widespread disease or later develop widespread non-small cell lung cancer may have chemotherapy which improves the chance of 12 months survival by 9%.
Radiotherapy is used to alleviate the symptoms from the primary cancer or other sites of disease, such as the bone.
Small cell lung cancer is primarily treated with chemotherapy. The best outcome is if the disease is confined to the chest but chemotherapy is still used in disease that is widespread at presentation. Radiotherapy may be used to consolidate the local chest area or to prevent metastases occurring in the brain. Radiotherapy can also be used for palliation of painful localised areas, such as in the bone.