When you or someone you care about has been diagnosed with prostate cancer it’s important to learn about the diagnostic tests involved in detecting prostate cancer. Understanding your diagnosis is an important part of the decision-making process.
A common system used by doctors to determine the stage of prostate cancer is the international TNM (tumour, node, metastasis) system. Cancer is staged according to:
T: the type of tumour
N: tumour spread to the lymph nodes (N for “nodes”)
M: tumour spread to distant sites (metastasis)
T1 (Stage A)
The tumour is small and confined to the prostate (not detectible during a digital rectal exam). This stage of prostate cancer usually produces no symptoms. Treatment may involve observation, radical prostatectomy to remove the prostate or radiation therapy
T2 (Stage B)
The tumour is confined to the prostate gland but may be detected during digital rectal exam. Possible symptoms may include a need to urinate frequently, especially at night. Treatment may involve radical prostatectomy or radiation therapy, possibly combined with hormonal therapy (to shrink the tumour).
T3 (Stage C)
The tumour has begun to spread beyond the prostate to areas surrounding the gland. Possible symptoms may include a need to urinate frequently, especially at night. Treatment may involve radiation therapy combined with hormonal therapy, or for some patients radical prostatectomy to remove the prostate.
T4 (Stage D1)
The tumour has spread beyond the prostate into surrounding structures including the pelvic lymph nodes (N+). Possible symptoms may include a need to urinate frequently, painful, obstructed urine flow (blood may appear in urine), and fatigue. Treatment may involve hormonal therapy, possibly with radiation therapy to ease symptoms
M+ (Stage D2)
When cancer has spread beyond the prostate it is said to have metastasized. Cancer may spread to distant sites such as bone, liver or lung via the lymphatic system and the blood supply. Cancer that has reached this stage may produce symptoms such as difficult or painful urination, obstructed urine flow, bone pain if the cancer has spread to the bone, and fatigue. Treatment for this stage of cancer is aimed at easing symptoms and slowing the progression of the disease. This usually includes hormonal therapy.
The tissue samples taken from your prostate during biopsy are examined under a microscope by a pathologist. A grade of one (low grade) to five (high grade) are assigned to the two most common patterns of cancer seen under the microscope:
1. How the cells look (on a scale of 1 to 5).
2. How the cells are arranged (on a scale of 1 to 5).
These two numbers are then combined to give a Gleason Grade score of 2-10.
This chart describes the type of cancer usually associated with each grade of cancer. A lower Gleason indicates a well differentiated, or a lower potential to spread. A higher Gleason grade indicates a poorly differentiated cancer, or more likely to spread. The Gleason grade may be an important factor in the doctors decision to recommend a radical prostatectomy to a patient.
Low Grade (2-4) Medium Grade (5-7) High Grade (8-10)
2 – 3 – 4 5 – 6 – 7 8 – 9 – 10
slow growth unpredictable growth aggressive growth
This is the least dangerous type of cancer. The cells look most like normal prostate cells and are described as being “well-differentiated”. This type of cancer tends to be slow growing.|Intermediate cancers may behave like low-grade or high-grade cancers. The cells’ behaviour may depend on the volume of the cancer and the PSA level. This is the most common grade of prostate cancer.|High-grade cancers are usually very aggressive and quick to spread to the tissue surrounding the prostate. These cancer cells look least like normal prostate cells and are usually described as “poorly-differentiated”.
Normal prostate tissue consists of a structured arrangement of small glands (acini) and ducts. This is a slide of Low Grade cancer. Low grade cancer is the least aggressive and most resembles normal tissue.
This is a slide of Medium Grade (6) cancer. As the cancer cells multiply and spread both the appearance and arrangement of the cells will change. The cells change shape and begin to look less like typical prostate cells. As well, this increase in activity causes the cell nucleus (it contains the genetic material for the maintenance, growth and reproduction of each cell) to become larger than normal.
All of these changes also cause the ducts and glands (acini) of the prostate to take on an irregular appearance.
This is a slide of High Grade cancer. These cancer cells tend to behave very aggressively. Normal cells die off as they compete against the cancer cells for nutrients. As High Grade cancer cells continue to spread, the ducts and glands (acini) of the prostate disappear also.
As part of the diagnostic process you may be expected to undergo additional tests to determine if cancer has spread beyond the prostate. This may include a CT scan.
CT scan, also called CAT scan, stands for Computerized Axial Tomography. It is a form of computerized X-ray that allows doctors to view your internal organs. A machine revolves around you generating a series of images that are then translated by a computer.
Prostate specific antigen (PSA) is an enzyme produced in the ducts of the prostate and absorbed into the bloodstream. Here it may become bound to two proteins: anti-chymotrypsin (ACT) and alpha macroglobulin (AMG). The “PSA test” measures the level of free and bound PSA in the blood. Combined, the digital rectal exam (DRE) and the PSA test are the most accurate guide to early detection of prostate cancer. You may also have heard of the prostatic acid phosphatase (PAP) blood test. This test is rarely performed, as it is less accurate than the PSA test.
Should I get a PSA test?
Normally, the level of PSA detected in the blood is between 0.0 and 4.0. An increase in the level of your PSA does not necessarily mean that you have prostate cancer, just as a low PSA level does not necessarily mean that you do not have prostate cancer. An elevated PSA may be caused by non-cancerous conditions such as benign prostatic hyperplasia, urinary tract infection, prostatitis or any other condition or diagnostic test that might irritate the prostate gland. PSA may even increase slightly after sexual intercourse.
Although an elevated PSA does not necessarily mean that you have cancer it is currently the most accurate indicator that something may be wrong and that further tests such as an ultrasound with biopsy should be performed.
Most men who have been diagnosed with prostate cancer have a PSA level greater than 4.0. Generally, the higher the PSA, the more serous or advanced the cancer. However, it is important to remember that numeric value given to your PSA level is not as important as fluctuations that may occur in your PSA level with additional testing.
Biopsy and Ultrasound
A transrectal ultrasound (TRUS) of the prostate is performed by placing a lubricated probe in the rectum. Sound waves emitted by the probe bounce off of the prostate and surrounding tissue and back to the probe. This allows a picture to be made that shows the prostate and its parts. It may also show areas where there is cancer.
It is standard to perform a biopsy using ultrasound guidance. In a prostate biopsy, tiny pieces of tissue are removed from the prostate using a small spring-loaded needle. The needle unit is attached to the ultrasound probe and enters the prostate through the rectum. Usually about 6 -12 prostatic tissue samples are obtained (sometimes more) and then examined under a microscope.
View of a Normal Prostate (photo to come)
This ultrasound image shows a normal prostate gland. This image was taken through a “transverse” section of the prostate. Simply put, this is a side-to-side view of the prostate. The probe sits at the bottom of the picture, placed in the rectum and directly beneath the prostate. The normal prostate is a symmetrical, crescent-shaped structure. From this angle we may also see the urethra, the tube that runs through the prostate carrying urine from the bladder out through the penis.
Normal Ultrasound (photo to come)
View of a Cancerous Prostate (photo to come)
In this ultrasound image we can see an enlarged darkened area in the lower right portion of the prostate. This proved to be cancer of the prostate. The cancerous tissue is darker because it is much more dense than the normal tissue. Notice also that the shape of the gland is much less symmetrical than the normal prostate. This is an advanced form of prostate cancer that has already spread through the capsule surrounding the prostate to the surrounding structures.
Abnormal utlrasound (photo to come)
If you’re dealing with prostate cancer, you’ll hear about Partin tables, which have become a valuable tool for doctors and patients.
The tables, developed by urologists Alan W. Partin, M.D., Ph.D., and Patrick C. Walsh, M.D., help doctors and patients decide upon the best course of treatment for prostate cancer.
It is difficult for urologists to predict what they might find during radical prostatectomy (surgery to remove the prostate). Surgery can cure prostate cancer only if the disease has not spread too far beyond the confines of the prostate. Before the Partin tables were developed, doctors could guess the extent of cancer spread, but they couldn’t be sure until they examined the patient’s pelvic lymph nodes in a procedure called pelvic lymph node dissection. And even then, microscopic bits of cancer, too small to be seen, could have strayed beyond the prostate.
Drs. Partin and Walsh correlated three documented types of information about a man’s prostate cancer:PSA level, Gleason grade and estimated clinical stage. Using these variables, they devised tables that provide a more accurate means of estimating, before surgery, the likelihood that the cancer had spread to the seminal vesicles, the pelvic lymph nodes or through the prostatic capsule. It is known that men whose cancer involves either the seminal vesicles or the pelvic lymph nodes rarely are cured by surgery. Having an accurate prediction of such involvement can help predict whether the surgery or radiation therapy is likely to be successful. However, it is important to note that while the Partin tables help predict what the surgeon will find during surgery, they have not been demonstrated to predict whether surgery will cure the patient.
How the Partin Coefficient Tables Work
The Partin coefficient tables can be used to offer estimates of four different items which may be very important in deciding how to treat a patient:
- The probability that the patient has completely organ-confined disease
- The probability that the patient has “established capsular penetration”, meaning that the patient’s prostate cancer has extended into and perhaps through the capsule of the prostate
- The probability that the patient has extension of his prostate cancer into his seminal vesicles
- The probability that the patient has prostate cancer which has spread into his lymph nodes
Let’s look at an example of how the Partin tables work. Suppose a man has a PSA of 7, a clinical stage T2a (a lump on one side of the prostate that can be felt during a digital rectal exam) and a Gleason score of 6. By using the Partin calculator (based on Partin tables), you would estimate that the man has a 50% chance of having disease confined to the prostate. A man with a PSA of 24, clinical stage T2a disease and a Gleason score of 7 has only an 11% chance of having organ-confined disease, with a 23% chance of having positive seminal vesicles.
As part of the diagnostic process you may be expected to undergo additional tests to determine if cancer has spread beyond the prostate. This may include a bone scan.
A bone scan is an imaging technique used to identify the presence of cancer in the bones. A tiny amount of radioactive substance is injected into your bloodstream and absorbed by your bones. If prostate cancer has spread to the bones, it most often shows up on the scan as a series of hot spots (darker areas) along the spine and ribs.