If cancer is found in the prostate, your doctor will need to assess the stage, or extent, of the disease. This process is called "staging" and attempts to identify if the cancer is localized to the prostate or if it has spread to other areas of the body. Knowing what stage your cancer is will help you make treatment decisions.
There are three ways that cancer spreads through the body:
When cancer from the prostate invades another tissue it will form what is called a secondary tumour. The primary tumour is in the tissue which is the source of the cancer. The secondary tumour is the result of metastasis, and is made of the same kind of cells as the primary tumour.
So, in the case of prostate cancer the primary tumour is in the prostate. If prostate cells spread to bone and form a tumour there, then this tumour is called the secondary tumour and it is made up of prostate cancer cells.
A common system used by doctors to classify the stage of prostate cancer is the TNM (tumor, node, metastasis) system. Cancer is staged according to:
T = the extent of the primary tumor (the tumour in the prostate)
N = if the tumor has spread to the lymph nodes (the nearest lymph nodes are biopsied for prostate cancer)
M = if the tumor has spread to distant sites (metastasis - have any secondary tumours formed?)
Your doctor can determine your clinical stage by administering some common tests. These include digital rectal exam (DRE), biopsy, bone scan, MRI, CT Scan, and PSA tests. You may not require all of these tests to stage your cancer. Your doctor will be sure to administer what is necessary.