CancerCare Manitoba
 
 
 
Diagnostic Tests

 
To help make an accurate diagnosis your physician will utilize the following examinations:
  • Digital Rectal Examination (DRE)
    Since the prostate is located just in front of the rectum, your doctor can feel it by inserting a lubricated gloved finger into the rectum. This is called a digital rectal examination (DRE). The presence of lumps or hardness within the prostate will suggest prostate cancer. Not all lumps in the prostate are cancerous and a biopsy will be done to confirm or exclude cancer. A DRE is performed in men presenting with symptoms of difficulty with urination. A DRE may also be performed during a general medical examination to try and detect the cancer before symptoms occur.
  • The PSA Blood Test
    PSA is a protein produced by the prostate and released in very small amounts into the bloodstream. When there's a problem with the prostate, such as when prostate cancer develops and grows, more and more PSA is released, until it reaches a level where it can be easily detected in the blood.

    To measure PSA, a small amount of blood is drawn, and the level of PSA is measured. PSA levels under 4 ng/mL are usually considered "normal," however, depending on the age of the man, what is considered normal may be lower than that.

    PSA can also be elevated if BPH or prostatis are present and some men with prostate cancer have "low" levels of PSA. This is why both the PSA and DRE are used to screen for the presence of disease and an abnormal result usually leads to a more accurate test, the prostate biopsy.
  • Biopsy
    During a biopsy, a needle is inserted into the prostate to take 12 to 14 small samples of tissue under the guidance of ultrasound imaging called transrectal ultrasound (TRUS).

    TRUS is not a test to screen for prostate cancer. It is performed in patients suspected of having cancer based on DRE or PSA. TRUS produces an image of the prostate and permits accurate placement of the biopsy needle into selected areas of the prostate. It is performed by inserting a probe just slightly larger than the index finger into the rectum.

    The biopsy procedure may cause some discomfort, however it is performed under local anaesthesia and most men do not report that it is painful. The samples are sent to the laboratory where they are examined by the pathologist where the sample is graded and scored (see Gleason Grading and Gleason Scores for more detailed information).

Gleason Grading and Gleason Scores

Normal 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 appearance 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 changed 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 through 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 in that sample, and a second Gleason grade to the next most common pattern. This is repeated for each of the samples taken from the prostate gland. The two grades are added, and the Gleason score, or sum, is determined for that sample.

Generally speaking, the Gleason score tends to predict the aggressiveness 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.

If the biopsy shows cancer then other tests may be done to check if it has spread including.
  • A bone scan involves injection of a radioisotope, which can demonstrate metastases to bone.
  • A CT scan is a special type of x-ray sometimes is done to assess spread to lymph nodes.