13.17 - Cancer

Benign and malignant tumours

• Cancer is a disease that arises when changes in a cell lead to abnormal, uncontrolled growth and division.
• These abnormal cells divide far faster than the body needs, building up into a mass of cells called a tumour.
• There are two types of tumour, and they behave very differently.

Benign tumours

• A growth of abnormal cells that stays contained in one area, usually held within a membrane (it is encapsulated).
• It grows until there is no more room, but does not invade or spread to other parts of the body.
• Not normally dangerous, and is not cancer.

Malignant tumours

• A malignant tumour is cancer, and its cells are not held in one place (it is not encapsulated).
• The tumour grows into and invades neighbouring healthy tissues.
• Cells can break off and be carried around the body in the bloodstream.
• Wherever these cells settle, they invade the tissue and grow into new tumours, called secondary tumours.
• Because malignant tumours spread and damage tissue throughout the body, they can be fatal.

Cancer risk factors

• Anyone can develop cancer. Having a risk factor doesn't mean a person will definitely get cancer - it only raises the chance.
• Risk factors fall into two groups: lifestyle factors and inherited faulty genes.

Lifestyle risk factors

• Smoking - Strongly linked to lung cancer.
• UV (ultraviolet) radiation - Too much exposure, from the Sun or from sunbeds, damages skin cells and increases the chance of skin cancer.
• Viral infection - Infection with certain viruses raises cancer risk. Infection with the human papilloma virus (HPV) is linked to cervical cancer, which the HPV vaccine helps protect against.

Inherited risk factors

• Not all risk factors are lifestyle choices.
• Some people inherit faulty genes that make them more susceptible to particular cancers, so cancer can run in families.

Cancer screening and treatments

• Catching cancer early greatly improves a patient's chance of survival, which is why screening programmes are used.
• Screening is designed to detect a cancer at the earliest possible stage - before it spreads - so treatment has the best chance of working.
• There are screening programmes for several cancers, including breast and cervical cancer.
• People are also encouraged to check themselves - looking for skin changes that could be early skin cancer, and for lumps in the testes.

Ways to treat cancer

• Surgery - Physically removes the tumour and usually has few side effects. It can't work if the cancer has already spread or sits somewhere that can't be reached.
• Radiotherapy - Uses high-energy X-rays or other radiation to kill cancer cells. It can be aimed accurately at cancers deep inside the body, but the radiation also damages nearby healthy cells.
• Chemotherapy - Uses drugs to kill cancer cells and can reach cancer anywhere in the body. It's a broad approach that affects healthy cells too, causing significant side effects such as nausea and hair loss.

Immunotherapy

• A more recent approach that uses the body's own immune system to fight the cancer.
• It involves injecting antibodies - usually special antibodies made in the laboratory - that attach specifically to antigens found only on the surface of cancer cells.
• Once attached, the antibodies act as markers, so phagocytes and other white blood cells can locate the cancer cells and destroy them.
• Because the antibodies target only cancer cells, immunotherapy tends to have fewer side effects than treatments such as radiotherapy and chemotherapy.