What tests can detect prostate cancer early?

The tests discussed below are used to look for warning signs of prostate cancer. But these early detection tests can’t tell for sure if you have cancer. If the result of one of these tests is abnormal, you will probably need a prostate biopsy to determine if you have cancer (see If prostate cancer screening test results aren’t normal).

Prostate-specific antigen (PSA) blood test

Prostate-specific antigen (PSA) is a substance made by cells in the prostate gland (both normal cells and cancer cells). PSA is mostly found in semen, but a small amount is also found in the blood.

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%.

If your PSA level is high, your doctor may advise either waiting a while and repeating the test, or getting a prostate biopsy to find out if you have cancer. 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.

Factors that might affect PSA levels

A number of factors other than prostate cancer can also raise PSA levels:

• An enlarged prostate: Conditions such as benign prostatic hyperplasia (BPH), a non-cancerous enlargement of the prostate that affects many men as they grow older, can raise PSA levels.
• Older age: PSA levels normally go up slowly as you get older, even if you have no prostate abnormality.
• Prostatitis: This term refers to infection or inflammation of the prostate gland, which can raise PSA levels.
• Ejaculation: This can make the PSA go up for a short time, and then go down again. This is why some doctors suggest that men abstain from ejaculation for a day or two before testing.
• Riding a bicycle: Some studies have suggested that cycling may raise PSA levels (possibly because the seat puts pressure on the prostate), although not all studies have found this.
• Certain urologic procedures: Some procedures done in a doctor’s office that affect the prostate, such as a prostate biopsy or cystoscopy, can result in higher PSA levels for a short time. Some studies have suggested that a digital rectal exam (DRE) might raise PSA levels slightly, although other studies have not found this. Still, if both a PSA test and a DRE are being done during a doctor visit, some doctors advise having the blood drawn for the PSA before having the DRE, just in case.
• Certain medicines: Taking male hormones like testosterone (or other medicines that raise testosterone levels) may cause a rise in PSA.

Some things might cause PSA levels to go down (even if a man has prostate cancer):

• 5-alfa reductase inhibitors: Certain drugsused to treat BPH or urinary symptoms, such as finasteride (Proscar or Propecia) or dutasteride (Avodart), may lower PSA levels. These drugs can also affect prostate cancer risk (discussed in Can prostate cancer be prevented?). Tell your doctor if you are taking these medicines because they may lower PSA levels, so the doctor might need to adjust the reading.
• Herbal mixtures: Some mixturesthat are sold as dietary supplements may also mask a high PSA level. This is why it’s important to let your doctor know if you are taking any type of supplement, even ones that are not necessarily meant for prostate health. Saw palmetto (an herb used by some men to treat BPH) does not seem to affect PSA.
• Obesity: Obese (very overweight) men tend to have lower PSA levels.
• Aspirin: Some research has suggested that men taking aspirin regularly may have lower PSA levels. This effect may be greater in non-smokers. More research is needed to confirm this finding. If you take aspirin regularly (for example, to help prevent heart disease), talk to your doctor before you stop taking it for any reason.
• Statins: Some studies have linked the long-term use of cholesterol-lowering drugs known as statins, such as atorvastatin (Lipitor), rosuvastatin (Crestor), and simvastatin (Zocor), with lower PSA levels.
• Thiazide diuretics: Thiazide diuretics, such as hydrochlorothiazide (HCTZ), are a type of water pill often used to treat high blood pressure. Taking a thiazide diuretic for years is linked to lower PSA levels.

For men not known to have prostate cancer, it’s not always clear if lowering the PSA is helpful. In some cases the factor that lowers the PSA may also lower a man’s risk of prostate cancer. But in other cases, it might lower the PSA level without affecting a man’s risk of cancer. This could actually be harmful, if it were to lower the PSA from an abnormal level to a normal one, as it might result in not detecting a cancer. This is why it’s important to talk to your doctor about anything that might affect your PSA level.

Special types of PSA tests

Some doctors might consider using different types of PSA tests (discussed below) to help decide if you need a prostate biopsy, but not all doctors agree on how to use these other PSA tests. If your PSA test result isn’t normal, ask your doctor to discuss your cancer risk and your need for further tests.

Percent-free PSA: PSA occurs in 2 major forms in the blood. One form is attached to blood proteins, while the other circulates free (unattached). The percent-free PSA (fPSA) is the ratio of how much PSA circulates free compared to the total PSA level. The percentage of free PSA is lower in men who have prostate cancer than in men who do not.

This test is sometimes used to help decide if you should have a prostate biopsy if your PSA results are in the borderline range (like between 4 and 10). A lower percent-free PSA means that your chance of having prostate cancer is higher and you should probably have a biopsy.

Many doctors recommend biopsies for men whose percent-free PSA is 10% or less, and advise that men consider a biopsy if it is between 10% and 25%. Using these cutoffs detects most cancers and helps some men avoid unnecessary prostate biopsies. This test is widely used, but not all doctors agree that 25% is the best cutoff point to decide on a biopsy, and the cutoff may change depending on the overall PSA level.

Complexed PSA: This test directly measures the amount of PSA that is attached to other proteins (the portion of PSA that is not “free”). This test could be done instead of checking the total and free PSA, and it could give the same amount of information as the other tests done separately. This test is being studied to see if it provides the same level of accuracy.

Tests that combine different types of PSA: Some newer tests, such as the prostate health index (phi) and the 4Kscore test, combine the results of different types of PSA to get an overall score that reflects the chance a man has prostate cancer. These tests might be useful in men with a slightly elevated PSA, to help determine if they should have a prostate biopsy. Some tests might be used to help determine if a man who has already had a prostate biopsy that didn’t find cancer should have another biopsy.

PSA velocity: The PSA velocity is not a separate test. It is a measure of how fast the PSA rises over time. Normally, PSA levels go up slowly with age. Some research has found that these levels go up faster if a man has cancer, but studies have not shown that the PSA velocity is more helpful than the PSA level itself in finding prostate cancer. For this reason, the ACS guidelines do not recommend using the PSA velocity as part of screening for prostate cancer.

PSA density: PSA levels are higher in men with larger prostate glands. The PSA density (PSAD) is sometimes used for men with large prostate glands to try to adjust for this. The doctor measures the volume (size) of the prostate gland with transrectal ultrasound (discussed in If prostate cancer screening test results aren’t normal) and divides the PSA number by the prostate volume. A higher PSA density indicates a greater likelihood of cancer. PSA density has not been shown to be as useful as the percent-free PSA test.

Age-specific PSA ranges: PSA levels are normally higher in older men than in younger men, even when there is no cancer. A PSA result within the borderline range might be very worrisome in a 50-year-old man but cause less concern in an 80-year-old man. For this reason, some doctors have suggested comparing PSA results with results from other men of the same age.

But because the usefulness of age-specific PSA ranges is not well proven, most doctors and professional organizations (as well as the makers of the PSA tests) do not recommend their use at this time.

Digital rectal exam (DRE)

For a digital rectal exam (DRE), the doctor inserts a gloved, lubricated finger into the rectum to feel for any bumps or hard areas on the prostate that might be cancer. As shown in the picture below, the prostate is just in front of the rectum. Prostate cancers often begin in the back part of the gland, which might be felt during a rectal exam. This exam can be uncomfortable (especially for men who have hemorrhoids), but it usually isn’t painful and only takes a short time.

DRE is less effective than the PSA blood test in finding prostate cancer, but it can sometimes find cancers in men with normal PSA levels. For this reason, it may be included as a part of prostate cancer screening.