With time, cells from the tumour can break off from the primary (original) tumour and enter the bloodstream or lymphatic system, spreading the cancer to nearby lymph nodes or other parts of the body. This may result in a separate tumour forming in another part of the body.
The liver is the most common site for bowel cancer cells to spread to because the blood supply to the bowel passes through the liver as it returns to the heart. The lungs are also a common site of metastases because of the high blood flow, which can carry cancerous cells from the bowel.
It is important to remember that metastases are formed by cancerous cells from the bowel growing in other organs, such as the liver or lungs. Therefore, the treatments used are specific to patients with bowel cancer and different to those used to treat lung cancer and liver cancer.