Treatment of cancer can include surgery, chemotherapy, radiation therapy or newer therapies such as using monoclonal antibodies.
Surgery involves removal of a tumour or the tissue in which it is found, for example, a lumpectomy where just the tumour is removed from a breast, or a mastectomy where the whole breast is removed. How successful the surgery is depends on whether or not the cancer has spread to other parts of the body. If it moves to a different part of the body, especially the lymph nodes, even a single cancer cell could grow into a new tumour and cause a recurrence of the cancer. A pathologist will examine the tissue that has been removed to determine the amount of normal tissue and the likelihood that there are other cancer cells still in the patient’s body.
Chemotherapy works by targeting cells that are dividing rapidly, by interfering with cell division or DNA synthesis. Chemotherapy can also affect normal tissue that is fast growing such as the hair follicles on your head or the lining of your intestines, leading to such side effects as hair loss or nausea.
Early after the discovery of X-rays, it was discovered that, along with other forms of ionising radiation, they could be used to treat cancers, by damaging the DNA in the cancer cell leading to the cell’s death. Cells are more vulnerable to dying when they are in the process of cell division, so tissues that are dividing rapidly, like cancer cells, are more likely to be killed. Ionising radiation also has an effect on normal cells, which can lead to side effects and the possibility of tumours. However, normal cells have better DNA repair mechanisms than cancer cells so the radiation treatment is carefully planned to give the normal tissue enough time to recover between treatments. Damage to normal tissue is also minimised by targeting the radiation as close to the tumour as possible. Modern radiation therapy techniques can use imaging technology to create a 3D model of the tumour and use this in the targeting of radiation beams. Radiation can also be given internally to a patient by inserting beads of a radioactive material directly into a tumour.
An emerging area of treatment uses the body’s own defences against the cancer. This includes the use of monoclonal antibodies, where a cell that is producing antibodies against a protein that is associated with cancer cells is cloned to create a cell line that is producing identical antibodies. The drug Herceptin is an example of the use of such antibodies. HER2 is a protein, found on the surface of normal breast cells that transmits the signal telling the breast cells to divide. In one type of breast cancer, there is an excessive amount of this protein on breast cells, which means the cells are bombarded with messages to divide. Herceptin is a monoclonal antibody targeting this protein. It seems to work in two ways – it stops the HER2 protein from transmitting the message to divide to the cell nucleus, and it marks the cell for destruction by the body’s immune system. Monoclonal antibodies can also be used to target cancer cells in chemotherapy or radiation therapy by attaching a radio nucleotide or chemotherapy drug to an antibody that is targeting a particular cancer protein.
Different types of therapies may be combined for greater effectiveness. For example, before surgery, chemotherapy or radiation therapy may be used to shrink the tumour to make it easier to remove, or after breast removal, a woman might be given Herceptin to mop up any HER2 positive cells that might have escaped and started to form a tumour elsewhere.