Testing Methods
How is prostate cancer detected?
Digital Rectal Exam (DRE): As the prostate is located just in front of the rectum, it can be felt by inserting a lubricated gloved finger into the rectum. A lump or hard area will suggest cancer. Not all lumps are cancerous, and a biopsy (tissue sample) will confirm or exclude cancer. A DRE should be performed in men with urinary symptoms, and at an annual physical exam.
PSA: Another way of detecting prostate cancer is by means of a blood test for prostate specific antigen (PSA). Only the prostate produces PSA. It can be detected in the blood and is normally present in small amounts. In most, but not all men with prostate cancer, blood levels of PSA are increased. Abnormal levels of PSA may indicate the need for a prostate biopsy even when the DRE is normal. However, an elevated PSA does not necessarily mean that prostate cancer is present as this can also occur in some patients with benign prostatic hyperplasia (BPH) or prostate infection (prostatitis). On the other hand, cancer may be present even with normal PSA levels. DRE is therefore important to detect these cancers. Approximately 70% of prostate cancers are detected because of an elevated PSA. Having an annual PSA test and DRE have been shown to increase the early detection of prostate cancer. The chance of curing prostate cancer may be increased if it is detected early. Because there is no definite proof that early detection is beneficial and because these tests may be abnormal in men who do not have prostate cancer, the decision as to whether men over 50 years old should have these tests performed annually is controversial. If you are in this age group, you should read the Canadian Prostate Health Council booklet on Prostate Specific Antigen and discuss the matter further with your physician http://www.canadian-prostate.com/.
Prostate Biopsy: A biopsy is a tissue sample taken to examine under the microscope. When there is a suspicion of prostate cancer, a biopsy is required to make the diagnosis. This is done by passing a small needle through the rectal wall, into the prostate. This is the only way to make a definitive diagnosis of cancer. This procedure is usually done with the guidance of transrectal ultrasound (TRUS). It is done using local anesthesia, as an outpatient. TRUS is only a guide for where to place the biopsy needle. It is not a test to screen for prostate cancer.
Other tests
A bone scan may be done if cancer is diagnosed, to check if the cancer has spread to bones. It is only of value if the PSA level is high (>20).
Other X-rays are of limited value, unless individually indicated.
CT scanning is used in the planning of Radiation treatment.
What is cancer "staging and grading"?
Staging refers to the extent of the cancer. It is based on 3 pieces of information:
T (tumor); N (nodes); M (metastases). The TNM classification is applied to all cancers.
N refers to lymph nodes. N0 means no lymph node invasion. N1, N2 etc means the number of nodes involved. Nx means the nodes have not been tested.
M refers to metastases (spread to other parts of the body, usually bone): M0 means no metastases, M+ means boney invasion. Mx means the bones have not been scanned (most cases).
Grading refers to the aggressiveness of the cancer cells. The Pathologist can tell how aggressive the cells are when examining the biopsy sample. The cells are given a score (Gleason) from 1 to 5, with the lower number indicating least aggressive. The most common and second commonest appearing cells are scored, and the numbers added together. This sum is the Gleason score: e.g. one area of 3, the other area 4; 3 + 4 = Gleason 7.
The higher the Gleason score, the more aggressive the cancer. Gleason 6 and 7 are the most common grades seen in practice.