Prostate cancer is suspected when a nodule or irregularity is found on rectal exam or a blood test shows a high or rising PSA (Prostate Specific Antigen). There may be symptoms, but since the PSA test became available in the early 1990s, it is not common for the cancer to be found at a later stage, once it causes symptoms. The healthcare provider who suspects prostate cancer will refer to a urologist for further evaluation. A urologist is a doctor who specializes in evaluation and treatment of diseases or conditions of the male urinary tract and genital structures.
After a thorough evaluation that can include a course of antibiotics and/or more testing, the urologist may recommend a prostate biopsy. This is the only way to know for sure if cancer is present. It is typically done by a urologist in his office. If the biopsy shows cancer, it is graded by how fast it is likely to grow and spread. Depending on the grade, more testing may be done to see if the cancer has spread already. This is called staging and it's important in determining how the cancer should be treated and the likelihood that it can be cured. The following is a basic overview of how prostate cancer is diagnosed, graded and staged.
History and Physical Exam for Prostate Cancer
The history consists of questions about your symptoms and risk factors for prostate cancer. Early stage prostate cancer rarely causes symptoms. However, as prostate cancer advances, one or more of the following might be present:
- Trouble having or keeping an erection (erectile dysfunction)
- Blood in the urine
- Pain in the bones such as hips, ribs, or back
- Weakness or numbness in legs or feet
- Loss of bladder or bowel control
The above symptoms may have other causes besides prostate cancer. Problems with urination such as frequency or a weak stream can be a sign of benign prostatic hyperplasia (BPH), a much less serious condition that is due to prostate enlargement that happens with aging.
Digital Rectal Exam (DRE)
The word "digital" as used above has nothing to do with analog… In this sense, "digit" means finger. During a DRE, the physician inserts a gloved, lubricated finger into the rectum and feels the prostate for any irregularities in size, shape, and texture. The DRE can distinguish between possible prostate cancer and non-cancerous conditions such as BPH. The DRE may be part of a routine physical exam in men 50 or older. If abnormalities are found, this triggers a referral to a urologist for further evaluation. The DRE is a test feared by many men. Though it is not the most pleasant experience, it should not hurt, takes only a few minutes, and it can provide valuable information.1
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, more PSA is released into the bloodstream. It eventually reaches a level where it can be easily detected with a blood test.
During a PSA test, a small amount of blood is drawn with a thin needle from a vein in the arm. The specimen is sent to a laboratory and the PSA is measured.
- Levels under 4 ng/mL are usually considered "normal"
- Levels over 10 ng/mL are usually considered "high"
- Levels between 4 and 10 ng/mL are usually considered "intermediate"
PSA is not a perfect test since it is not specific to cancer. Levels can be elevated if other prostate problems are present, such as BPH or prostatitis (infection of the prostate). Some men with prostate cancer may even have low levels of PSA. PSA can also be falsely lower or diluted in men who are overweight or obese, due to a larger blood volume. 2
Medications used to reduce the size of the prostate, such as Avodart, may falsely lower PSA by as much as 50%. PSA alone is not enough to determine the presence or absence of prostate cancer, but it is very useful in determining the need for a prostate biopsy.
PSA velocity is the change in PSA level over time. A sharp rise in the PSA level raises the suspicion of cancer and may indicate a fast-growing cancer.
PSA density considers the relationship between the level of PSA and the size of the prostate to adjust for prostate enlargement. An elevated PSA can be due to prostate enlargement rather than cancer but cancer can not necessarily be ruled out.
The percent-free PSA can be determined by dividing the amount of "free" or unbound PSA by the total PSA. Studies have shown that men tend to have lower levels of free PSA when prostate cancer is present. The percent free PSA is usually above 25%. Between 10% and 25% is considered intermediate, while below 10% is low. If your PSA is in the borderline range (4-10 ng/ml), a percent-free PSA of 10% or less means that your likelihood of having prostate cancer is about 50% and a biopsy will probably be recommended. Because there are some concerns with the accuracy of percent-free PSA, one being that it is less stable than bound PSA, it is not often used. The urologist decides using his clinical judgment whether it will provide useful information based on the individual case. It does not hurt to ask, however, if it would be helpful in your case to determine the need for a biopsy.3
Prostate Biopsy
When prostate cancer is suspected, the only way to find out if cancer is present is a biopsy of the prostate gland. Before the biopsy, the man gives himself an enema at home and antibiotics are started to prevent infection. Any blood thinning medications such as aspirin or coumadin are discontinued for several days before the biopsy to lessen the chances of bleeding.
The procedure takes about 30 minutes and is done in a side-lying position, most often in the urologist's office. It is uncomfortable, but usually not painful. A rectal probe is inserted into the rectum. It sends out sound waves (ultrasound) which can't be heard but the computer uses the echoes to create an image on a screen. This allows the urologist to determine the location of the samples in real time.
Samples are taken from both sides of the prostate gland and areas where cancer is more likely to occur are focused on. There will be some blood in the urine and bowel movement that day and possibly the next day. There may be blood in the semen for several months after the biopsy. Approximately 12 samples of prostate tissue are taken through a needle in a spring-loaded biopsy gun under the guidance of transrectal ultrasound (TRUS).
Chances are high that the biopsy will be negative. About 15% of men with a PSA lower than 4 and 25 percent of men with a PSA level between 4 and 10 will have a positive biopsy. There are also false negatives, meaning that the biopsy is negative because the cancer was missed in the samples that were taken.1
The pathology report will provide a Gleason Score, how many samples were positive, what percentage of those samples were positive, and where the positive samples are located.
The Gleason Score can be difficult to understand. Scores range from 2-10, but are most often between 6 and 9. The higher the number, the less the cells look like normal prostate cells and the more likely the cancer is to grow and spread quickly.1 These scores are usually expressed as 3+3 or 4+3. A 4+3 would be more aggressive than a 3+4. The following picture shows how the cells look under a microscope and what the scores would be. In real life, it is not this simplistic. Prostate cancer pathology is difficult to read. Therefore, getting a second read on the pathology can provide helpful information.
Other important information found on biopsy includes:
- The number of samples taken and the number which are positive
- The percentage of cancer found in each of the positive cores
- Whether the cancer is on one side of the prostate or both (bilateral)4
Bone Scan
The bones are the most likely site of distant spread of prostate cancer. If prostate cancer is diagnosed at an early stage, a bone scan may not be done because of the low risk that the cancer has spread to the bone. There are guidelines that physicians can follow to determine if a bone scan should be done (National Comprehensive Cancer Network guidelines). If the PSA is below 10, the Gleason score is 7 or less, there is no bone pain, and the clinical stage is less than T3, a bone scan is rarely performed. However, this is a clinical judgment by your physician. He should explain why he is ordering a bone scan or why it is not necessary.
In a bone scan, radioactive tracers are injected into the bloodstream. These tracers are attracted to bone. Pictures are taken of the bones using a gamma camera. The tracer accumulates where there is a healing fracture or cancer, showing up as a "hot spot". A bone scan can only detect cancer that is large enough. It also may give a false positive if there is an old fracture, arthritis or infection.4
CT Scan
A CT scan of the abdomen and pelvis is sometimes done to detect spread of prostate cancer. The CT is a special type of x-ray which is a series of pictures taken from many angles. You will lie on a table inside a ring-shaped machine. It can be done with or without an intravenous dye that is injected into your vein or you might be asked to swallow 1-2 pints of a liquid contrast. CT is not good at visualizing cancer in the prostate gland but it may show possible cancer in the pelvic lymph nodes in more advanced cancer. It also has a false positive rate in diagnosing cancer in the seminal vesicles. It is rarely used in men with localized disease but may be used if spread to the lymph nodes is suspected. The National Comprehensive Cancer Network (NCCN) guidelines are another tool that can be used by the physician to determine the usefulness of a CT scan.1,4
MRI Scan (Magnetic Resonance Imaging)
An MRI gives three-dimensional images that are like slices of anatomy. It provides more information than the CT scan. An average scan takes about 45 minutes. Since the person is inside the machine, this test can feel claustrophobic to some patients. There are open MRIs available.
An MRI takes longer than a CT scan, sometimes up to an hour. It can also be done using a rectal coil which stays in place for 30-45 minutes.1,4 The T3 MRI is more recently being used for staging of prostate cancer. It is an MRI with a stronger magnet and provides more detailed information. The MRI is not used routinely to stage prostate cancer and is based on the clinical judgment of the urologist or radiation oncologist (a physician who treats cancer with radiation).
Prostascint™ Scan
Similar to a bone scan, this scan uses low levels of a radioactive substance injected into your vein to find cancer that has spread to pelvic lymph nodes or other organs. You will lie on a table while a special camera takes pictures of your body. This is done about ½ hour after the injection and again 3-5 days later. The usefulness of this test has not yet been decided and it is rarely used when prostate cancer is first diagnosed.4
Staging of Prostate Cancer
Tumor stage reflects the size and spread of the cancer. The system used for staging is the TNM system (Tumor, Nodes and Metastasis).
- T1a-c means that the DRE is normal.
- T2a-c means that the DRE is abnormal but there are no signs of cancer outside the prostate.
- The N0 stage means there is no sign of cancer spread to the lymph nodes near the prostate.
- The M0 stage means there is no sign of spread to distant organs.
There are two types of staging, clinical or pathological. Clinical stage is the physician's best guess of the extent of the disease based on all the information he has about the cancer. If you have surgery, the structures and tissues removed can be examined in a pathology lab. The pathological stage can be different than the clinical stage and it is more accurate.4,5
When you are diagnosed with prostate cancer, the three most important things to know about your cancer are your highest PSA, your Gleason score and the clinical stage. You may hear other terms such as PSA density and PSA velocity that are also considered when determining the aggressiveness of the cancer.
New tests being developed and studied for both diagnosing and staging prostate cancer. All of these tests help you and your doctor know the location and extent of the cancer when deciding on possible treatment options.
References
- Walsh, Patrick C. Dr. Patrick Walsh's Guide to Surviving Prostate Cancer, 2nd ed. 2007.
- National Cancer Institute Fact Sheet:PSA
http://www.cancer.gov/cancertopics/factsheet/Detection/PSA - Bostwick, D.G., E. D, Crawford, C. S. Higano, M. Roach III: American Cancer Society's
Complete Guide to Prostate Cancer, 2005. - American Cancer Society: Prostate Cancer Overview, 2009.
- The American Urological Association: The Management of Localized Prostate Cancer, 2008.
This article has been reviewed by a member of the Wellness Partners Editorial Board.
Posted March 2011
