What is Cancer?

The body is made up of millions of tiny building blocks called cells. These cells then group together to form tissues and organs within our bodies. Normal, healthy cells grow and divide in a controlled fashion, creating new cells. This enables the body to grow, repair and heal. The cell stops reproducing and dies naturally when it’s old and no longer needed.

Cancer develops when these normal cells become abnormal. The abnormal cells do not stop reproducing, but keep making new abnormal cells uncontrollably. These abnormal cells eventually group together to form a tumour. Not all tumours are cancerous and non-cancerous tumours are called benign tumours. A benign tumour may grow but will not spread to anywhere else in the body. It may cause problems if it puts pressure on nearby organs.

A cancerous tumour is called a malignant tumour. It can grow into nearby tissue and invade surrounding organs. Sometimes, cancer cells spread from where the cancer first started (the primary site) to other parts of the body. They can travel through the blood or lymphatic system.

When the cancerous cells reach another part of the body, they may begin to reproduce and form another tumour. This is called a secondary cancer or a metastasis.

For more information on what radiotherapy is and how it works, please see:What is radiotherapy?