Can prostate cancer be found early?
Screening refers to testing to find a disease such as cancer in people who do not have symptoms of that disease. For some types of cancer, screening can help find cancers at an early stage, when they are more easily cured.
Prostate cancer can often be found early by testing the amount of prostate-specific antigen (PSA) in a man's blood. Another way to find prostate cancer is the digital rectal exam (DRE), in which the doctor puts a gloved finger into the rectum to feel the prostate gland. These 2 tests are described later on in more detail.
If the results of either one of these tests are abnormal, further testing is needed to see if there is a cancer. If prostate cancer is found as a result of screening with the PSA test or DRE, it will probably be at an earlier, more treatable stage than if no screening were done.
Since the use of early detection tests for prostate cancer became fairly common in the United States (about 1990), the prostate cancer death rate has dropped. But it isn't yet clear if this drop is a direct result of screening or if it might be caused by something else, like improvements in treatment.
There is no question that screening can help find many prostate cancers early, but there are limits to the prostate cancer screening tests used today. Neither the PSA test nor the DRE is 100% accurate. These tests can sometimes have abnormal results even when a man does not have cancer (known as false positive results). Normal results can also occur even when a man does have cancer (known as false negative results). Unclear test results can cause confusion and anxiety. False-positive results can lead some men to have a prostate biopsy (with small risks of pain, infection, and bleeding) when they do not have cancer. And false-negative results can give some men a false sense of security even though they actually have cancer.
Another important issue is that even if screening detects a cancer, doctors often can't tell if the cancer is truly dangerous. Finding and treating all prostate cancers early might seem as if it would always be a good thing. But some prostate cancers grow so slowly that they would probably never cause problems. Because of an elevated PSA level, some men may be diagnosed with a prostate cancer that they would have never even known about at all. It would never have lead to their death, or even caused any symptoms.
But these men may still be treated with either surgery or radiation, either because the doctor can't be sure how quickly the cancer might grow and spread, or because the men are uncomfortable knowing they have cancer and not getting any treatment. Treatments like surgery and radiation can have urinary, bowel, and/or sexual side effects that may seriously affect a man's quality of life.
Men and their doctors may end up struggling over whether they need treatment or whether they might be able to be followed without being treated right away (an approach called watchful waiting or active surveillance). Even when men are not treated right away, they still need regular blood tests and prostate biopsies to determine the need for future treatment. These tests are linked with risks of anxiety, pain, infection, and bleeding.
To help figure out if prostate cancer screening is worthwhile, doctors are conducting large studies to see if early detection tests will lower the risk of death from prostate cancer. The most recent results from 2 large studies were conflicting, and didn't offer clear answers.
Early results from a study done in the United States found that annual screening with PSA and DRE detected more prostate cancers than in men not screened, but it did not lower the death rate from prostate cancer. A European study did find a lower risk of death from prostate cancer with PSA screening (done about once every 4 years), but the researchers estimated that about 1,050 men would need to invited to be screened (and 37 treated) to prevent one death from prostate cancer. Neither of these studies has shown that PSA screening helps men live longer (lowered the overall death rate).
Prostate cancer is often a slow-growing cancer, so the effects of screening in these studies may become clearer in the coming years. Both of these studies are being continued to see if longer follow-up will give clearer results. Several other large studies of prostate cancer screening are now going on as well.
At this time, the American Cancer Society (ACS) recommends that men thinking about prostate cancer screening should make informed decisions based on available information, discussion with their doctor, and their own views on the benefits and side effects of screening and treatment (see below).
Until more information is available, you and your doctor can decide whether you should have tests to screen for prostate cancer. There are many factors to take into account, including your age and health. If you are young and develop prostate cancer, it may shorten your life if it is not caught early. Screening men who are older or in poor health in order to find early prostate cancer is less likely to help them live longer. This is because most prostate cancers are slow-growing, and men who are older or sicker are likely to die from other causes before their prostate cancer grows enough to cause problems.
American Cancer Society recommendations for the early detection of prostate cancer
The American Cancer Society recommends that men have a chance to make an informed decision with their health care provider about whether to be screened for prostate cancer. The decision should be made after getting information about the uncertainties, risks, and potential benefits of prostate cancer screening. Men should not be screened unless they have received this information.
The discussion about screening should take place at age 50 for men who are at average risk of prostate cancer and are expected to live at least 10 more years.
This discussion should take place starting at age 45 for men at high risk of developing prostate cancer. This includes African-American men and men who have a first-degree relative (father, brother, or son) diagnosed with prostate cancer at an early age (younger than age 65).
This discussion should take place at age 40 for men at even higher risk (those with more than one first-degree relative who had prostate cancer at an early age).
After this discussion, those men who want to be screened should be tested with the prostate-specific antigen (PSA) blood test. The digital rectal exam (DRE) may also be done as a part of screening.
If, after this discussion, a man is unable to decide if testing is right for him, the screening decision can be made by the health care provider, who should take into account the patient’s general health preferences and values.
Assuming no prostate cancer is found as a result of screening, the time between future screenings depends on the results of the PSA blood test:
- Men who have a PSA less than 2.5 ng/ml may only need to be retested every 2 years.
- Screening should be done yearly for men whose PSA level is 2.5 ng/ml or higher.
Because prostate cancer often grows slowly, men without symptoms of prostate cancer who do not have a 10-year life expectancy should not be offered testing since they are not likely to benefit. Overall health status, and not age alone, is important when making decisions about screening.
Even after a decision about testing has been made, the discussion about the pros and cons of testing should be repeated as new information about the benefits and risks of testing becomes available. Further discussions are also needed to take into account changes in the patient's health, values, and preferences.
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 healthy men have 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 biopsy. Men with a borderline 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 more than 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 (see the section, “How is prostate cancer diagnosed?”). Not all doctors use the same PSA cutoff point when advising whether to do a biopsy. Some may advise it if the PSA is 4 or higher, while others might recommend it at 2.5 or higher. Other factors, such as your age, race, and family history, may also come into play.
Factors that might affect PSA levels
The PSA level can also be increased by things other than prostate cancer, such as:
- An enlarged prostate: Conditions such as benign prostatic hyperplasia (BPH), a non-cancerous enlargement of the prostate that many men get as they grow older, may 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 may raise PSA levels.
- Ejaculation: This can cause the PSA to go up for a short time, and then go down again. This is why some doctors suggest that men abstain from ejaculation for 2 days 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, may 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 testosterone (or other medicines that raise testosterone levels) may cause a rise in PSA.
Some things may cause PSA levels to go down (even if cancer is present):
- Certain medicines: Certain drugs used to treat BPH or urinary symptoms, such as finasteride (Proscar or Propecia) or dutasteride (Avodart), may lower PSA levels. You should tell your doctor if you are taking these medicines, because they will lower PSA levels and require the doctor to adjust the reading.
- Herbal mixtures: Some mixtures that are sold as dietary supplements may also mask a high PSA level. This is why it is 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 men tend to have lower PSA levels.
- Aspirin: Some recent research has suggested that men who take 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 (such as to help prevent heart disease), talk to your doctor before you stop taking it for any reason.
For men not known to have prostate cancer, it is 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 is important to talk to your doctor about anything that might affect your PSA level.
Newer types of PSA tests
Some doctors might consider using newer types of PSA tests to help determine if you need a prostate biopsy, but not all doctors agree on how to use these other PSA tests. If your PSA test result is not normal, ask your doctor to discuss your cancer risk and your need for further tests.
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 (between 4 and 10). A lower percent-free PSA means that your likelihood 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 PSA level.
A newer test, known as complexed PSA, measures the amount of PSA that is attached to other proteins. This test is described in more detail in the section, "What's new in prostate cancer research and treatment?"
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 guideline does not recommend using the PSA velocity as part of screening for prostate cancer.
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 "How is prostate cancer diagnosed?") and divides the PSA number by the prostate volume. A higher PSA density (PSAD) 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.
Other uses of the PSA blood test
The PSA test is used mainly to detect prostate cancer early, but it is also useful if prostate cancer has been diagnosed. For more information on the other uses of PSA testing, see the sections "How is prostate cancer diagnosed?" and "Following PSA levels during and after treatment."
Digital rectal exam (DRE)
For a digital rectal exam (DRE), a doctor inserts a gloved, lubricated finger into the rectum to feel for any bumps or hard areas on the prostate that might be cancer. The prostate gland is just in front of the rectum, and most cancers begin in the back part of the gland, which can be felt during a rectal exam. This exam can be uncomfortable (especially in 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.
The DRE can also be used once a man is known to have prostate cancer to try to determine if it might have spread to nearby tissues and to detect cancer that has come back after treatment.
Last Medical Review: 02/27/2012
Last Revised: 05/15/2013