Although the DRE and PSA tests cannot diagnose prostate cancer, they can signal the require for a biopsy to examine the prostate cells and decide whether they are cancerous. In some men, changes in urinary or sexual function lead to a full evaluation by the doctor, and, if prostate cancer is assumed, a biopsy will be performed.
During a biopsy, needles are inserted into the prostate to take small samples of tissue, often under the guidance of ultrasound imaging. The biopsy procedure may cause some discomfort or pain, but the procedure is short, and can usually be performed without an overnight hospital stay.
Gleason Grading and Gleason Scores
Under normal conditions, prostate cells, just like all other cells in the body, are constantly reproducing and dying, and each new prostate cell has the same shape and facade as all of the other prostate cells. But cancer cells look different, and the degree to which they look different from normal cells is what determines the cancer grade. "Low-grade" tumor cells tend to look very similar to normal cells, whereas "high-grade" tumor cells have mutated so much that they often barely resemble the normal cells.
The Gleason grading system accounts for the five distinct patterns that prostate tumor cells tend to go during as they change from normal cells. The scale runs from 1 to 5, where 1 represents cells that are very nearly normal, and 5 represents cells that don’t look much like prostate cells at all.
After examining the cells under a microscope, the pathologist looking at the biopsy sample assigns one Gleason grade to the most common pattern, and a second Gleason grade to the next most common pattern. The two grades are added, and the Gleason score, or sum, is determined.
Generally speaking, the Gleason score tends to predict the assertiveness of the disease and how it will behave. The higher the Gleason score, the less the cells behave like normal cells, and the more aggressive the tumor tends to be.
Staging the Disease
Staging determines the extent of prostate cancer. Localized prostate cancer means that the cancer is confined within the prostate. Locally advanced prostate cancer means that most of the cancer is confined within the prostate, but some has started to escape to the immediate surrounding tissues. In metastatic disease, the prostate cancer is growing outside the prostate and its immediate environs, possibly to more distant organs.
A number of tests can be used to help determine the stage of disease. For example, cancers growing outside of the prostate can often be detected through traditional imaging studies, such as CT scans, MRIs, or x-rays, or through more specialized imaging tests such as bone scans. Note that because these tests cannot detect very small groups of cancer cells, results of these tests cannot be used alone to determine the stage of the disease, to guide treatment options, or to predict outcomes.
Metastatic disease can also be detected through imaging studies, and often can be detected in the lymph nodes. Cancers that spread to more distant organs tend to travel through the lymph system, a circulatory system similar to the blood surgery, lymph nodes will be removed and examined for the presence of cancer cells.
Knowing the stage of disease can help to determine how aggressively the disease needs to be treated, and how likely it is to be eradicated by the available treatment options.