Usually, the cancer will be fully diagnosed and characterized before radiation therapy begins. This characterization may include the cancer type, that is, the cell type from which the cancer originated. For example, a brain tumor may be diagnosed...

as an astrocytoma if the original cell type was an astrocyte (a type of cell in the brain). Also, the cancer cells will be studied to find out how abnormal they are. Very aggressive cancers that are prone to metastasis (spread) look very different then in their natural state. Less developed cancers will look more like the native cell. Once the cancer has been fully characterized (a cell type is determined, the stage and or grade is determined, and the extent of spread) then radiation therapy can applied appropriately. Also various X-rays/CT scans/MRI exams will be done to determine the extent of the cancer and used to compare with scans done after radiation therapy.

 

There is a significant amount of planning and preparation involved prior to the actual administration of radiotherapy. If a patient is going to receive external beam radiation, doctors may perform a simulation exercise to determine the precise location of the beam’s effects. During the simulation, special X-rays are taken through a treatment port to assess the precise depth of radiation therapy. Often patients will need more than one treatment port to deliver radiation from different angles on the body. Sometime sensitizers are administered that make the radiation therapy more deadly to the tumor.

 

Prior to brachytherapy or internal radiation, extensive imaging is done to the tumor/area to be treated. For example, if prostate cancer is going to be treated with radioactive seed placement, a volume study is performed in advance. This provides a detailed picture of the prostate gland so that a minimum number of seeds can be placed that will still treat the entire area.

 

When systemic radiation therapy is planned, the cancerous region may need to be studied to determine blood flow and uptake rates. Since the radioactive substance needs to travel through the blood to the target organ, that organ must be able to absorb the radiation treatment.