Tests for Prostate Cancer
Most prostate cancers are first found during screening with a prostate-specific antigen (PSA) blood test or a digital rectal exam (DRE). (See Prostate Cancer Prevention and Early Detection.) Early prostate cancers usually don’t cause symptoms, but more advanced cancers are sometimes first found because of symptoms they cause.
If cancer is suspected based on results of screening tests or symptoms, tests will be needed to confirm the diagnosis. The actual diagnosis of prostate cancer can only be made with a prostate biopsy.
Medical history and physical exam
If your doctor suspects you might have prostate cancer, he or she will ask you about any symptoms you are having, such as any urinary or sexual problems, and how long you have had them. You might also be asked about possible risk factors, including your family history.
Your doctor will also examine you. This might include a digital rectal exam (DRE), during which the doctor’s gloved, lubricated finger is inserted into your rectum to feel for any bumps or hard areas on the prostate that might be cancer. If you do have cancer, the DRE can sometimes help tell if it’s only on one side of the prostate, if it’s on both sides, or if it’s likely to have spread beyond the prostate to nearby tissues.
Your doctor may also examine other areas of your body. He or she might then order some tests.
PSA blood test
The prostate-specific antigen (PSA) blood test is used mainly to screen for prostate cancer in men without symptoms (see Prostate Cancer Prevention and Early Detection). It’s also one of the first tests done in men who have symptoms that might be caused by prostate cancer.
Most men without prostate cancer have PSA levels under 4 nanograms per milliliter (ng/mL) of blood. The chance of having prostate cancer goes up as the PSA level goes up.
When prostate cancer develops, the PSA level usually goes above 4. Still, a level below 4 does not guarantee that a man doesn’t have cancer. About 15% of men with a PSA below 4 will have prostate cancer on a biopsy.
Men with a PSA level between 4 and 10 have about a 1 in 4 chance of having prostate cancer. If the PSA is more than 10, the chance of having prostate cancer is over 50%.
When considering whether to do a prostate biopsy to look for cancer, not all doctors use the same PSA cutoff point. Some may advise it if the PSA is 4 or higher, while others might recommend it starting at a lower level, such as 2.5 or 3. Other factors, such as your age, race, and family history, may affect this decision.
The PSA test can also be useful if you have already been diagnosed with prostate cancer.
- In men just diagnosed with prostate cancer, the PSA test can be used together with physical exam results and tumor grade (determined on the biopsy, described further on) to help decide if other tests (such as CT scans or bone scans) are needed.
- The PSA test is a part of staging (determining the stage of your cancer) and can help tell if your cancer is likely to still be confined to the prostate gland. If your PSA level is very high, your cancer is more likely to have spread beyond the prostate. This may affect your treatment options, since some forms of therapy (such as surgery and radiation) are not likely to be helpful if the cancer has spread to the lymph nodes, bones, or other organs.
- PSA tests are also an important part of monitoring prostate cancer during and after treatment (see Following PSA Levels During and After Treatment).
Transrectal ultrasound (TRUS)
For this test, a small probe about the width of a finger is lubricated and placed in your rectum. The probe gives off sound waves that enter the prostate and create echoes. The probe picks up the echoes, and a computer turns them into a black and white image of the prostate.
The procedure often takes less than 10 minutes and is done in a doctor’s office or outpatient clinic. You will feel some pressure when the probe is inserted, but it is usually not painful. The area may be numbed before the procedure.
TRUS is often used to look at the prostate when a man has a high PSA level or has an abnormal DRE result. It is also used during a prostate biopsy to guide the needles into the correct area of the prostate.
TRUS is useful in other situations as well. It can be used to measure the size of the prostate gland, which can help determine the PSA density (described in Prostate Cancer Prevention and Early Detection) and may also affect which treatment options a man has. TRUS is also used as a guide during some forms of treatment such as brachytherapy (internal radiation therapy) or cryotherapy.
If certain symptoms or the results of tests such as a PSA blood test or DRE suggest that you might have prostate cancer, your doctor will do a prostate biopsy.
A biopsy is a procedure in which small samples of the prostate are removed and then looked at under a microscope. A core needle biopsy is the main method used to diagnose prostate cancer. It is usually done by a urologist, a surgeon who treats cancers of the genital and urinary tract, which includes the prostate gland.
Using TRUS to “see” the prostate gland, the doctor quickly inserts a thin, hollow needle through the wall of the rectum and into the prostate. When the needle is pulled out it removes a small cylinder (core) of prostate tissue. This is repeated several times. Most urologists will take about 12 core samples from different parts of the prostate.
Though the procedure sounds painful, each biopsy usually causes only a brief uncomfortable sensation because it is done with a special spring-loaded biopsy instrument. The device inserts and removes the needle in a fraction of a second. Most doctors who do the biopsy will numb the area first by injecting a local anesthetic alongside the prostate. You might want to ask your doctor if he or she plans to do this.
The biopsy itself takes about 10 minutes and is usually done in the doctor’s office. You will likely be given antibiotics to take before the biopsy and possibly for a day or 2 after to reduce the risk of infection.
For a few days after the procedure, you may feel some soreness in the area and will probably notice blood in your urine. You may also have some light bleeding from your rectum, especially if you have hemorrhoids. Many men notice blood in their semen or have rust colored semen, which can last for several weeks after the biopsy, depending on how often you ejaculate.
Your biopsy samples will be sent to a lab, where they will be looked at a microscope to see if they contain cancer cells. If cancer is seen, it will also be assigned a grade (see the next section). Getting the results (in the form of a pathology report) usually takes at least 1 to 3 days, but it can sometimes take longer.
Even when taking many samples, biopsies can still sometimes miss a cancer if none of the biopsy needles pass through it. This is known as a false-negative result. If your doctor still strongly suspects you have prostate cancer (because your PSA level is very high, for example) a repeat biopsy might be needed to help be sure.
Grade (Gleason score) of prostate cancer
Prostate cancers are graded according to the Gleason system. This system assigns a Gleason grade based on how much the cancer looks like normal prostate tissue.
- If the cancer looks a lot like normal prostate tissue, a grade of 1 is assigned.
- If the cancer looks very abnormal, it is given a grade of 5.
- Grades 2 through 4 have features in between these extremes.
Most cancers are grade 3 or higher, and grades 1 and 2 are not often used.
Since prostate cancers often have areas with different grades, a grade is assigned to the 2 areas that make up most of the cancer. These 2 grades are added to yield the Gleason score (also called the Gleason sum).
There are some exceptions to this rule. If the highest grade takes up most (95% or more) of the biopsy sample, the grade for that area is counted twice as the Gleason score. Also, if 3 grades are present in a biopsy core, the highest grade is always included in the Gleason score, even if most of the core is taken up by areas of cancer with lower grades.
The Gleason score can be between 2 and 10, but most are at least a 6. The higher the Gleason score, the more likely it is that the cancer will grow and spread quickly.
Aside from the Gleason score, the grade of the cancer is sometimes expressed using other terms:
- Cancers with a Gleason score of 6 or less may be called well-differentiated or low-grade.
- Cancers with a Gleason score of 7 may be called moderately-differentiated or intermediate-grade.
- Cancers with Gleason scores of 8 to 10 may be called poorly-differentiated or high-grade.
Other information in a pathology report
Along with the grade of the cancer (if it is present), the pathology report often contains other information about the cancer, such as:
- The number of biopsy core samples that contain cancer (for example, “7 out of 12”)
- The percentage of cancer in each of the cores
- Whether the cancer is on one side (left or right) of the prostate or both sides (bilateral)
Sometimes when the prostate cells are seen, they don’t look like cancer, but they’re not quite normal, either. These results are often reported as suspicious.
Prostatic intraepithelial neoplasia (PIN): In PIN, there are changes in how the prostate cells look, but the abnormal cells don’t look like they’ve grown into other parts of the prostate (like cancer cells would). PIN is often divided into 2 groups:
- Low-grade PIN: the patterns of prostate cells appear almost normal
- High-grade PIN: the patterns of cells look more abnormal
Many men begin to develop low-grade PIN at an early age but don’t necessarily develop prostate cancer. The importance of low-grade PIN in relation to prostate cancer is still unclear. If low-grade PIN is reported on a prostate biopsy, the follow-up for patients is usually the same as if nothing abnormal was seen.
If high-grade PIN is found on a biopsy, there is about a 20% chance that cancer may already be present somewhere else in the prostate gland. This is why doctors often watch men with high-grade PIN carefully and may advise a repeat prostate biopsy, especially if the original biopsy did not take samples from all parts of the prostate.
Atypical small acinar proliferation (ASAP): This is sometimes just called atypia. In ASAP, the cells look like they might be cancerous when viewed under the microscope, but there are too few of them to be sure. If ASAP is found, there’s a high chance that cancer is also present in the prostate, which is why many doctors recommend getting a repeat biopsy within a few months.
Proliferative inflammatory atrophy (PIA): In PIA, the prostate cells look smaller than normal, and there are signs of inflammation in the area. PIA is not cancer, but researchers believe that PIA may sometimes lead to high-grade PIN or to prostate cancer directly.
For more information about how prostate biopsy results are reported, see the Prostate Pathology section of our website.
Imaging tests to look for prostate cancer spread
Imaging tests use x-rays, magnetic fields, sound waves, or radioactive substances to create pictures of the inside of your body.
If you are found to have prostate cancer, your doctor will use your digital rectal exam (DRE) results, prostate-specific antigen (PSA) level, and Gleason score from the biopsy results to figure out how likely it is that the cancer has spread outside your prostate. This information is used to decide if any imaging tests need to be done to look for possible cancer spread. Men with a normal DRE result, a low PSA, and a low Gleason score may not need any other tests because the chance that the cancer has spread is so low.
The imaging tests used most often to look for prostate cancer spread include:
If prostate cancer spreads to distant sites, it often goes to the bones first. A bone scan can help show whether cancer has reached the bones.
For this test, you are injected with a small amount of low-level radioactive material, which settles in damaged areas of bone throughout the body. A special camera detects the radioactivity and creates a picture of your skeleton.
A bone scan may suggest cancer in the bone, but to make an accurate diagnosis, other tests such as plain x-rays, CT or MRI scans, or even a bone biopsy might be needed.
Computed tomography (CT) scan
A CT scan uses x-rays to make detailed, cross-sectional images of your body. This test isn’t often needed for newly diagnosed prostate cancer if the cancer is likely to be confined to the prostate based on other findings (DRE result, PSA level, and Gleason score). Still, it can sometimes help tell if prostate cancer has spread into nearby lymph nodes. If your prostate cancer has come back after treatment, the CT scan can often tell if it is growing into other organs or structures in your pelvis.
CT scans are not as useful as magnetic resonance imaging (MRI) for looking at the prostate gland itself.
Magnetic resonance imaging (MRI)
Like CT scans, MRI scans show detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays. A contrast material called gadolinium may be injected into a vein before the scan to better see details.
MRI scans can give a very clear picture of the prostate and show if the cancer has spread outside the prostate into the seminal vesicles or other nearby structures. This can be very important in determining your treatment options. But like CT scans, MRI scans aren’t usually needed for newly diagnosed prostate cancers that are likely to be confined to the prostate based on other factors.
To improve the accuracy of the MRI, you might have a probe, called an endorectal coil, placed inside your rectum for the scan. This can be uncomfortable. If needed, medicine to make you feel sleepy (sedation) can be given before the scan.
Lymph node biopsy
In a lymph node biopsy, also known as lymph node dissection or lymphadenectomy, one or more lymph nodes are removed to see if they have cancer cells. This isn’t done very often for prostate cancer, but can be used to find out if the cancer has spread from the prostate to nearby lymph nodes.
Biopsy during surgery to treat prostate cancer
The surgeon may remove lymph nodes in the pelvis during the same operation as the removal of the prostate, which is known as a radical prostatectomy (see Surgery for Prostate Cancer).
If there is more than a very small chance that the cancer might have spread (based on factors such as a high PSA level or a high Gleason score), the surgeon may remove some lymph nodes before removing the prostate gland.
Sometimes the nodes will be looked at right away, while you are still under anesthesia, to help the surgeon decide whether to continue with the radical prostatectomy. This is called a frozen section exam because the tissue sample is frozen before thin slices are taken to check under a microscope. If the nodes contain cancer cells, the operation might be stopped (leaving the prostate in place). This could happen if the surgeon feels that removing the prostate would be unlikely to cure the cancer, but would still probably result in serious complications or side effects.
More often (especially if the chance of cancer spread is low), a frozen section exam is not done. Instead the lymph nodes and the prostate are removed and are then sent to the lab to be looked at. The lab results are usually available several days after surgery.
Lymph node biopsy as a separate procedure
A lymph node biopsy is rarely done as a separate procedure. It’s sometimes used when a radical prostatectomy isn’t planned (such as for some men who choose treatment with radiation therapy), but when it’s still important to know if the lymph nodes contain cancer.
Laparoscopic biopsy: A laparoscope is a long, slender tube with a small video camera on the end that is inserted into the abdomen through a small cut. It lets the surgeon see inside the abdomen and pelvis without needing to make a large cut (incision). Other small incisions are made to insert long instruments to remove the lymph nodes around the prostate gland, which are then sent to the lab.
Because there are no large incisions, most people recover fully in only 1 or 2 days, and the operation leaves very small scars.
Fine needle aspiration (FNA): If your lymph nodes appear enlarged on an imaging test (such as a CT or MRI scan) a doctor may take a sample of cells from an enlarged node by using a technique called fine needle aspiration (FNA).
To do this, the doctor uses a CT scan image to guide a long, hollow needle through the skin in the lower abdomen and into the enlarged node. The skin is numbed with local anesthesia before inserting the needle. A syringe attached to the needle lets the doctor take a small tissue sample from the node, which is then sent to the lab to look for cancer cells.
You will be able to return home a few hours after the procedure.
Last Medical Review: February 16, 2016 Last Revised: March 11, 2016